Ceramic materials, abrasive particles, abrasive articles, and methods of making and using the same

ABSTRACT

Amorphous materials, glass-ceramics and methods of making the same. Embodiments of the invention include abrasive particles. The abrasive particles can be incorporated into a variety of abrasive articles, including bonded abrasives, coated abrasives, nonwoven abrasives, and abrasive brushes.

This application is a continuation-in-part of U.S. Ser. Nos. 09/922,526,09/922,527, 09/922,528, and 09/922,530, filed Aug. 2, 2001, thedisclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to amorphous materials and glass-ceramics. Inanother aspect, embodiments of the present invention relates to abrasiveparticles and abrasive articles incorporating the abrasive particlestherein.

DESCRIPTION OF RELATED ART

A large number of amorphous (including) glass and glass-ceramiccompositions are known. The majority of oxide glass systems utilizewell-known glass-formers such as SiO₂, B₂O₃, P₂O₅, GeO₂, TeO₂, As₂O₃,and V₂O₅ to aid in the formation of the glass. Some of the glasscompositions formed with these glass-formers can be heat-treated to formglass-ceramics. The upper use temperature of glasses and glass-ceramicsformed from such glass formers is generally less than 1200° C.,typically about 700–800° C. The glass-ceramics tend to be moretemperature resistant than the glass from which they are formed.

In addition, many properties of known glasses and glass-ceramics arelimited by the intrinsic properties of glass-formers. For example, forSiO₂, B₂O₃, and P₂O₅-based glasses and glass-ceramics, the Young'smodulus, hardness, and strength are limited by such glass-formers. Suchglass and glass-ceramics generally have inferior mechanical propertiesas compared, for example, to Al₂O₃ or ZrO₂. Glass-ceramics having anymechanical properties similar to that of Al₂O₃ or ZrO₂ would bedesirable.

Although some non-conventional glasses such as glasses based on rareearth oxide-aluminum oxide (see, e.g., PCT application havingpublication No. WO 01/27046 A1, published Apr. 19, 2001, and JapaneseDocument No. JP 2000-045129, published Feb. 15, 2000) are known,additional novel glasses and glass-ceramic, as well as use for bothknown and novel glasses and glass-ceramics is desired.

In another aspect, a variety of abrasive particles (e.g., diamondparticles, cubic boron nitride particles, fused abrasive particles, andsintered, ceramic abrasive particles (including sol-gel-derived abrasiveparticles) known in the art. In some abrading applications, the abrasiveparticles are used in loose form, while in others the particles areincorporated into abrasive products (e.g., coated abrasive products,bonded abrasive products, non-woven abrasive products, and abrasivebrushes). Criteria used in selecting abrasive particles used for aparticular abrading application include: abrading life, rate of cut,substrate surface finish, grinding efficiency, and product cost.

From about 1900 to about the mid-1980's, the premier abrasive particlesfor abrading applications such as those utilizing coated and bondedabrasive products were typically fused abrasive particles. There are twogeneral types of fused abrasive particles: (1) fused alpha aluminaabrasive particles (see, e.g., U.S. Pat. No. 1,161,620 (Coulter), U.S.Pat. No. 1,192,709 (Tone), U.S. Pat. No. 1,247,337 (Saunders et al.),U.S. Pat. No. 1,268,533 (Allen), and U.S. Pat. No. 2,424,645 (Baumann etal.) and (2) fused sometimes also referred to as “co-fused”)alumina-zirconia abrasive particles (see, e.g., U.S. Pat. No. 3,891,408(Rowse et al.), U.S. Pat. No. 3,781,172 (Pett et al.), U.S. Pat. No.3,893,826 (Quinan et al.), U.S. Pat. No. 4,126,429 (Watson), U.S. Pat.No. 4,457,767 (Poon et al.), and U.S. Pat. No. 5,143,522 (Gibson etal.))(also see, e.g., U.S. Pat. No. 5,023,212 (Dubots et al.) and U.S.Pat. No. 5,336,280 (Dubots et al.) which report the certain fusedoxynitride abrasive particles). Fused alumina abrasive particles aretypically made by charging a furnace with an alumina source such asaluminum ore or bauxite, as well as other desired additives, heating thematerial above its melting point, cooling the melt to provide asolidified mass, crushing the solidified mass into particles, and thenscreening and grading the particles to provide the desired abrasiveparticle size distribution. Fused alumina-zirconia abrasive particlesare typically made in a similar manner, except the furnace is chargedwith both an alumina source and a zirconia source, and the melt is morerapidly cooled than the melt used to make fused alumina abrasiveparticles. For fused alumina-zirconia abrasive particles, the amount ofalumina source is typically about 50–80 percent by weight, and theamount of zirconia, 50–20 percent by weight zirconia. The processes formaking the fused alumina and fused alumina abrasive particles mayinclude removal of impurities from the melt prior to the cooling step.

Although fused alpha alumina abrasive particles and fusedalumina-zirconia abrasive particles are still widely used in abradingapplications (including those utilizing coated and bonded abrasiveproducts, the premier abrasive particles for many abrading applicationssince about the mid-1980's are sol-gel-derived alpha alumina particles(see, e.g., U.S. Pat. No. 4,314,827 (Leitheiser et al.), U.S. Pat. No.4,518,397 (Leitheiser et al.), U.S. Pat. No. 4,623,364 (Cottringer etal.), U.S. Pat. No. 4,744,802 (Schwabel), U.S. Pat. No. 4,770,671(Monroe et al.), U.S. Pat. No. 4,881,951 (Wood et al.), U.S. Pat. No.4,960,441 (Pellow et al.), U.S. Pat. No. 5,139,978 (Wood), U.S. Pat. No.5,201,916 (Berg et al.), U.S. Pat. No. 5,366,523 (Rowenhorst et al.),U.S. Pat. No. 5,429,647 (Larmie), U.S. Pat. No. 5,547,479 (Conwell etal.), U.S. Pat. No. 5,498,269 (Larmie), U.S. Pat. No. 5,551,963(Larmie), and U.S. Pat. No. 5,725,162 (Garg et al.)).

The sol-gel-derived alpha alumina abrasive particles may have amicrostructure made up of very fine alpha alumina crystallites, with orwithout the presence of secondary phases added. The grinding performanceof the sol-gel-derived abrasive particles on metal, as measured, forexample, by life of abrasive products made with the abrasive particleswas dramatically longer than such products made from conventional fusedalumina abrasive particles.

Typically, the processes for making sol-gel-derived abrasive particlesare more complicated and expensive than the processes for makingconventional fused abrasive particles. In general, sol-gel-derivedabrasive particles are typically made by preparing a dispersion or solcomprising water, alumina monohydrate (boehmite), and optionallypeptizing agent (e.g., an acid such as nitric acid), gelling thedispersion, drying the gelled dispersion, crushing the dried dispersioninto particles, screening the particles to provide the desired sizedparticles, calcining the particles to remove volatiles, sintering thecalcined particles at a temperature below the melting point of alumina,and screening and grading the particles to provide the desired abrasiveparticle size distribution. Frequently a metal oxide modifier(s) isincorporated into the sintered abrasive particles to alter or otherwisemodify the physical properties and/or microstructure of the sinteredabrasive particles.

There are a variety of abrasive products (also referred to “abrasivearticles”) known in the art. Typically, abrasive products include binderand abrasive particles secured within the abrasive product by thebinder. Examples of abrasive products include: coated abrasive products,bonded abrasive products, nonwoven abrasive products, and abrasivebrushes.

Examples of bonded abrasive products include: grinding wheels, cutoffwheels, and honing stones. The main types of bonding systems used tomake bonded abrasive products are: resinoid, vitrified, and metal.Resinoid bonded abrasives utilize an organic binder system (e.g.,phenolic binder systems) to bond the abrasive particles together to formthe shaped mass (see, e.g., U.S. Pat. No. 4,741,743 (Narayanan et al.),U.S. Pat. No. 4,800,685 (Haynes et al.), U.S. Pat. No. 5,037,453(Narayanan et al.), and U.S. Pat. No. 5,110,332 (Narayanan et al.)).Another major type are vitrified wheels in which a glass binder systemis used to bond the abrasive particles together mass (see, e.g., U.S.Pat. No. 4,543,107 (Rue), U.S. Pat. No. 4,898,587 (Hay et al.), U.S.Pat. No. 4,997,461 (Markhoff-Matheny et al.), and U.S. Pat. No.5,863,308 (Qi et al.)). These glass bonds are usually matured attemperatures between 900° C. to 1300° C. Today vitrified wheels utilizeboth fused alumina and sol-gel-derived abrasive particles. However,fused alumina-zirconia is generally not incorporated into vitrifiedwheels due in part to the thermal stability of alumina-zirconia. At theelevated temperatures at which the glass bonds are matured, the physicalproperties of alumina-zirconia degrade, leading to a significantdecrease in their abrading performance. Metal bonded abrasive productstypically utilize sintered or plated metal to bond the abrasiveparticles.

The abrasive industry continues to desire abrasive particles andabrasive products that are easier to make, cheaper to make, and/orprovide performance advantage(s) over conventional abrasive particlesand products.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides amorphous materialcomprising at least 35 (in some embodiments, preferably at least 40, 45,50, 55, 60, 65, or even at least 70) percent by weight Al₂O₃, based onthe total weight of the amorphous material, and a metal oxide other thanAl₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, andcomplex metal oxides thereof), wherein the amorphous material containsnot more than 10 (in some embodiments preferably, less than 5, 4, 3, 2,1, or even zero) percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the amorphousmaterial, wherein the amorphous material has x, y, and z dimensions eachperpendicular to each other, and wherein each of the x, y, and zdimensions is at least 5 mm (in some embodiments, at least 10 mm).Optionally, the amorphous material is heat-treated such that at least aportion of the amorphous material is converted to a glass-ceramic.

The x, y, and z dimensions of a material are determined either visuallyor using microscopy, depending on the magnitude of the dimensions. Thereported z dimension is, for example, the diameter of a sphere, thethickness of a coating, or the longest length of a prismatic shape.

In one aspect, the present invention provides amorphous materialcomprising at least 35 (in some embodiments, preferably at least 40, 45,50, 55, 60, 65, or even at least 70) percent by weight Al₂O₃, based onthe total weight of the amorphous material, and a metal oxide other thanAl₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, andcomplex metal oxides thereof), wherein the amorphous material containsnot more than 10 (in some embodiments preferably, less than 5, 4, 3, 2,1, or even zero) percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the amorphousmaterial, with the proviso that if the metal oxide other than Al₂O₃ isCaO or ZrO₂, then the amorphous material further comprises a metal oxideother than Al₂O₃, CaO, and ZrO₂ at least a portion of which forms adistinct crystalline phase when the amorphous material is crystallized.In some embodiments, the amorphous material has x, y, and z dimensionseach perpendicular to each other, and wherein each of the x, y, and zdimensions is at least 5 mm (in some embodiments, at least 10 mm).Optionally, the amorphous material is heat-treated such that at least aportion of the amorphous material is converted to a glass-ceramic.

A “distinct crystalline phase” is a crystalline phase that is detectableby x-ray diffraction as opposed to a phase that is present in solidsolution with another distinct crystalline phase. For example, it iswell known that oxides such as Y₂O₃ or CeO₂ may be in solid solutionwith a crystalline ZrO₂ and serve as a phase stabilizer. The Y₂O₃ orCeO₂ in such instances is not a distinct crystalline phase.

In some embodiments, the amorphous material comprises 0 to 70, 0 to 50,0 to 25, or even 0 to 10 percent by weight of the metal oxide other thanAl₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, andcomplex metal oxides thereof), and/or 0 to 50, 0 to 25, or even 0 to 10percent by weight of at least one of ZrO₂ or HfO₂, based on the totalweight of the amorphous material.

In some embodiments, the amorphous material may present in anothermaterial (e.g., particles comprising the amorphous material according tothe present invention, ceramic comprising the amorphous materialaccording to the present invention, etc.). Optionally, the amorphousmaterial (including a glass) is heat-treated such at least a portion ofthe amorphous material is converted to a glass-ceramic.

In another aspect, the present invention provides glass comprising atleast 35 (in some embodiments, preferably at least 40, 45, 50, 55, 60,65, or even at least 70) percent by weight Al₂O₃, based on the totalweight of the glass, and a metal oxide other than Al₂O₃ (e.g., Y₂O₃,REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex metal oxidesthereof), wherein the glass contains not more than 10 (in someembodiments preferably, less than 5 or even zero) percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thetotal weight of the glass, wherein the glass has x, y, and z dimensionseach perpendicular to each other, and wherein each of the x, y, and zdimensions is at least at least 5 mm (in some embodiments, at least 10mm). In some embodiments, the glass may present in another material(e.g., particles comprising the glass according to the presentinvention, ceramic comprising the glass according to the presentinvention, etc.). Optionally, the glass is heat-treated such that atleast a portion of the glass is converted to a glass-ceramic.

In another aspect, the present invention provides glass comprising atleast 35 (in some embodiments, preferably at least 40, 45, 50, 55, 60,65, or even at least 70) percent by weight Al₂O₃, based on the totalweight of the glass, and a metal oxide other than Al₂O₃ (e.g., Y₂O₃,REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex metal oxidesthereof), wherein the glass contains not more than 10 (in someembodiments preferably, less than 5 or even zero) percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thetotal weight of the glass, with the proviso that if the metal oxideother than Al₂O₃ is CaO, then the glass further comprises a metal oxideother than Al₂O₃ or CaO at least a portion of which forms a distinctcrystalline phase when the glass is crystallized. In some embodiments,the glass has x, y, and z dimensions each perpendicular to each other,and wherein each of the x, y, and z dimensions is at least at least 5 mm(in some embodiments, at least 10 mm). In some embodiments, the glassmay present in another material (e.g., particles comprising the glassaccording to the present invention, ceramic comprising the glassaccording to the present invention, etc.). Optionally, the glass isheat-treated such that at least a portion of the glass is converted to aglass-ceramic.

In some embodiments, the glass comprises 0 to 70, 0 to 50, 0 to 25, oreven 0 to 10 percent by weight of the metal oxide other than Al₂O₃(e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complexmetal oxides thereof), and/or 0 to 50, 0 to 25, or even 0 to 10 percentby weight of at least one of ZrO₂ or HfO₂, based on the total weight ofthe glass.

In another aspect, the present invention provides a method for making anarticle comprising glass comprising at least 35 (in some embodiments,preferably at least 40, 45, 50, 55, 60, 65, or even at least 70) percentby weight Al₂O₃, based on the total weight of the glass, and a metaloxide other than Al₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO,NiO, CuO, and complex metal oxides thereof), wherein the glass containsnot more than 10 (in some embodiments preferably, less than 5, 4, 3, 2,1, or even zero) percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, P₂O₅, TeO₂, and V₂O₅, based on the total weight of the glass, themethod comprising:

-   -   providing glass particles comprising at least 35 (in some        embodiments, preferably at least 40, 45, 50, 55, 60, 65, or even        at least 70) percent by weight Al₂O₃, based on the total weight        of the glass, and a metal oxide other than Al₂O₃ (e.g., Y₂O₃,        REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex metal        oxides thereof), wherein the glass contains not more than 10 (in        some embodiments preferably, less than 5, 4, 3, 2, 1, or even        zero) percent by weight As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and        V₂O₅, based on the total weight of the glass, the glass having a        T_(g);    -   heating the glass particles above the T_(g) such that the glass        particles coalesce to form a shape; and    -   cooling the shape to provide the article, with the proviso that        if the metal oxide other than Al₂O₃ is CaO or ZrO₂, then the        glass further comprises a metal oxide other than Al₂O₃ or CaO at        least a portion of which forms a distinct crystalline phase when        the glass is crystallized. Optionally, glass comprising the        article is heat-treated such that at least a portion of the        glass is converted to a glass-ceramic. In some embodiments, the        glass and glass-ceramic comprise 0 to 70, 0 to 50, 0 to 25, or        even 0 to 10 percent by weight of the metal oxide other than        Al₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO,        and complex metal oxides thereof), and/or 0 to 50, 0 to 25, or        even 0 to 10 percent by weight of at least one of ZrO₂ or HfO₂,        based on the total weight of the glass and glass-ceramic,        respectively.

In another aspect, the present invention provides a method for makingglass particles, the method comprising:

-   -   atomizing a glass melt comprising at least 35 (in some        embodiments, preferably at least 40, 45, 50, 55, 60, 65, or even        at least 70) percent by weight Al₂O₃, based on the total weight        of the glass melt, and a metal oxide other than Al₂O₃ (e.g.,        Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex        metal oxides thereof), wherein the glass melt contains not more        than 10 (in some embodiments preferably, less than 5 or even        zero) percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,        SiO₂, TeO₂, and V₂O₅, based on the total weight of the glass        melt; and    -   cooling the atomized glass melt to provide glass particles        comprising at least 35 (in some embodiments, preferably at least        40, 45, 50, 55, 60, 65, or even at least 70) percent by weight        Al₂O₃, based on the total weight of each glass particle, and a        metal oxide other than Al₂O₃, wherein each glass particle        contains not more than 10 (in some embodiments preferably, less        than 5 or even zero) percent by weight collectively As₂O₃, B₂O₃,        GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of        each glass particle, wherein the glass has x, y, and z        dimensions each perpendicular to each other, and wherein each of        the x, y, and z dimensions is at least 5 mm (in some        embodiments, at least 10 mm), with the proviso that if the metal        oxide other than Al₂O₃ is CaO or ZrO₂, then the glass further        comprises a metal oxide other than Al₂O₃ or CaO at least a        portion of which at least a portion of which forms a distinct        crystalline phase when the glass is crystallized. Optionally,        the glass is heat-treated such that at least a portion of the        glass is converted to a glass-ceramic. In some embodiments, the        glass and glass-ceramic comprise 0 to 50, 0 to 25, or even 0 to        10 percent by weight of the metal oxide other than Al₂O₃ (e.g.,        Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex        metal oxides thereof), and/or 0 to 50, 0 to 25, or even 0 to 10        percent by weight of at least one of ZrO₂ or HfO₂, based on the        total weight of the glass and glass-ceramic, respectively.

In another aspect, the present invention provides a glass-ceramiccomprising at least 35 (in some embodiments, preferably at least 40, 45,50, 55, 60, 65, or even at least 70) percent by weight Al₂O₃, based onthe total weight of the glass-ceramic, and a metal oxide other thanAl₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, andcomplex metal oxides thereof), wherein the glass-ceramic contains notmore than 10 (in some embodiments preferably, less than 5, 4, 3, 2, 1,or even zero) percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the glass-ceramic,wherein the glass-ceramic has x, y, and z dimensions each perpendicularto each other, and wherein each of the x, y, and z dimensions is atleast 5 mm (in some embodiments, at least 10 mm), with the proviso thatif the metal oxide other than Al₂O₃ is CaO, then the glass-ceramicfurther comprises crystals of a metal oxide other than CaO. In someembodiments, the glass-ceramic may present in another material (e.g.,particles comprising the glass-ceramic according to the presentinvention, ceramic comprising the glass-ceramic according to the presentinvention, etc.). In some embodiments, the glass-ceramic comprises 0 to50, 0 to 25, or even 0 to 10 percent by weight of the metal oxide otherthan Al₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, andcomplex metal oxides thereof), and/or 0 to 50, 0 to 25, or even 0 to 10percent by weight of at least one of ZrO₂ or HfO₂, based on the totalweight of the glass-ceramic.

In another aspect, the present invention provides a method for makingglass-ceramic, the method comprising heat-treating amorphous material(including glass) according to the present invention such that at leasta portion of the amorphous material is converted to a glass-ceramic.

In another aspect, the present invention provides a method for makingabrasive particles, the method comprising:

-   -   heat-treating amorphous material (including a glass) according        to the present invention such that at least a portion of the        amorphous material is converted to a glass-ceramic; and    -   crushing the glass-ceramic to provide abrasive particles        comprising the glass-ceramic.

The abrasive particles can be incorporated into an abrasive article, orused in loose form. Abrasive articles according to the present inventioncomprise binder and a plurality of abrasive particles, wherein at leasta portion of the abrasive particles are the abrasive particles accordingto the present invention. Exemplary abrasive products include coatedabrasive articles, bonded abrasive articles (e.g., wheels), non-wovenabrasive articles, and abrasive brushes. Coated abrasive articlestypically comprise a backing having first and second, opposed majorsurfaces, and wherein the binder and the plurality of abrasive particlesform an abrasive layer on at least a portion of the first major surface.

In some embodiments, preferably, at least 5, 10, 15, 20, 25, 30, 35, 40,45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or even 100 percent byweight of the abrasive particles in an abrasive article are the abrasiveparticles according to the present invention, based on the total weightof the abrasive particles in the abrasive article.

Abrasive particles are usually graded to a given particle sizedistribution before use. Such distributions typically have a range ofparticle sizes, from coarse particles fine particles. In the abrasiveart this range is sometimes referred to as a “coarse”, “control” and“fine” fractions. Abrasive particles graded according to industryaccepted grading standards specify the particle size distribution foreach nominal grade within numerical limits. Such industry acceptedgrading standards (i.e., specified nominal grades) include those knownas the American National Standards Institute, Inc. (ANSI) standards,Federation of European Producers of Abrasive Products (FEPA) standards,and Japanese Industrial Standard (JIS) standards. In one aspect, thepresent invention provides a plurality of abrasive particles having aspecified nominal grade, wherein at least a portion of the plurality ofabrasive particles are abrasive particles according to the presentinvention. In some embodiments, preferably, at least 5, 10, 15, 20, 25,30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or even 100percent by weight of the plurality of abrasive particles are theabrasive particles according to the present invention, based on thetotal weight of the plurality of abrasive particles.

In another aspect, the present invention provides a method for makingabrasive particles according to the present invention, the methodcomprising heat-treating particles comprising the amorphous material(including glass) according to the present invention such that at leasta portion of the amorphous material converts to a glass-ceramic providethe abrasive particles comprising the glass-ceramic. Typically, theabrasive particles comprising the glass-ceramic are graded afterheat-treating to provide a plurality of abrasive particles having aspecified nominal grade, wherein at least a portion of the plurality ofabrasive particles is a plurality of the abrasive particles comprisingthe glass-ceramic. Optionally, prior to the heat-treating the particlesthe amorphous material, a plurality of particles having a specifiednominal grade is provided, wherein at least a portion of the particlesis a plurality of the particles comprising the amorphous material to beheat-treated, and wherein the heat-treating is conducted such that aplurality of abrasive particles having a specified nominal grade isprovided, wherein at least a portion of the abrasive particles is aplurality of the abrasive particles comprising the glass-ceramic.

In another aspect, the present invention provides a method for makingabrasive particles according to the present invention, the methodcomprising heat-treating particles comprising the amorphous materialsuch that at least a portion of the amorphous material converts to aglass-ceramic to provide the abrasive particles comprising theglass-ceramic. Typically, the abrasive particles comprising theglass-ceramic are graded after heat-treating to provide a plurality ofabrasive particles having a specified nominal grade, wherein at least aportion of the plurality of abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic. Optionally, prior tothe heat-treating the particles comprising the amorphous material, aplurality of particles having a specified nominal grade is provided,wherein at least a portion of the particles is a plurality of theparticles comprising the amorphous material to be heat-treated, andwherein the heat-treating is conducted such that a plurality of abrasiveparticles having a specified nominal grade is provided, wherein at leasta portion of the abrasive particles is a plurality of the abrasiveparticles comprising the glass-ceramic.

In another aspect, the present invention provides a plurality ofabrasive particles having a specified nominal grade, wherein at least aportion of the abrasive particles is a plurality of abrasive particlescomprising a glass-ceramic, the glass-ceramic comprising at least 35 (insome embodiments, preferably at least 40, 45, 50, 55, 60, 65, or even atleast 70) percent by weight Al₂O₃, based on the total weight of theglass-ceramic of each particle of the portion, and a metal oxide otherthan Al₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, andcomplex metal oxides thereof), wherein the glass-ceramic contains notmore than 10 (in some embodiments preferably, less than 5, 4, 3, 2, 1,or even zero) percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the glass-ceramic ofeach particle of the portion. In some embodiments, the glass-ceramiccomprise 0 to 50, 0 to 25, or even 0 to 10 percent by weight of themetal oxide other than Al₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃,MgO, NiO, CuO, and complex metal oxides thereof), and/or 0 to 50, 0 to25, or even 0 to 10 percent by weight of at least one of ZrO₂ or HfO₂,based on the total weight of the glass-ceramic. In some embodiments, theglass-ceramic has x, y, and z dimensions each perpendicular to eachother, and wherein each of the x, y, and z dimensions is at least 25micrometers, 30 micrometers, 35 micrometers, 40 micrometers, 45micrometers, 50 micrometers, 75 micrometers, 100 micrometers, 150micrometers, 200 micrometers, 250 micrometers, 500 micrometers, 1000micrometers, 2000 micrometers, 2500 micrometers, 1 mm, 5 mm, or even atleast 10 mm. In some embodiments, if the metal oxide other than Al₂O₃ isCaO, then the glass-ceramic further comprises at least one distinctcrystalline phase of a metal oxide other than CaO. In some embodiments,if the metal oxide other than Al₂O₃ is ZrO₂, then the glass-ceramicfurther comprises at least one distinct crystalline phase of a metaloxide other than ZrO₂. In some embodiments, if the metal oxide otherthan Al₂O₃ is CaO or ZrO₂, then the glass-ceramic further comprises atleast one distinct crystalline phase of a metal oxide other than CaO orZrO₂.

In another aspect, the present invention provides a method for makingabrasive particles, the method comprising:

-   -   providing a plurality of particles having a specified nominal        grade, wherein at least a portion of the particles is a        plurality of particles comprising an amorphous material, the        amorphous material comprising at least 35 (in some embodiments,        preferably at least 40, 45, 50, 55, 60, 65, or even at least 70)        percent by weight Al₂O₃, based on the total weight of the        amorphous material of each particle of the portion, and a metal        oxide other than Al₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃,        MgO, NiO, CuO, and complex metal oxides thereof), wherein the        amorphous material contains not more than 10 (in some        embodiments preferably, less than 5 or even zero) percent by        weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and        V₂O₅, based on the total weight of the amorphous material of        each particle of the portion; and    -   heat-treating the particles comprising the amorphous material        such that at least a portion of the amorphous material is        converted to a glass-ceramic and such that a plurality of        abrasive particles having a specified nominal grade is provided,        wherein at least a portion of the abrasive particles is a        plurality of abrasive particles comprising the glass-ceramic. In        some embodiments, the glass and glass-ceramic comprise 0 to 50,        0 to 25, or even 0 to 10 percent by weight of the metal oxide        other than Al₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO,        NiO, CuO, and complex metal oxides thereof), and/or 0 to 50, 0        to 25, or even 0 to 10 percent by weight of at least one of ZrO₂        or HfO₂, based on the total weight of the glass and        glass-ceramic, respectively.

In another aspect, the present invention provides a method for makingabrasive particles, the method comprising:

-   -   heat-treating particles comprising an amorphous material such        that at least a portion of the glass is converted to a        glass-ceramic, the amorphous material comprising at least 35 (in        some embodiments, preferably at least 40, 45, 50, 55, 60, 65, or        even at least 70) percent by weight Al₂O₃, based on the total        weight of the amorphous material of each particle of the        portion, and a metal oxide other than Al₂O₃ (e.g., Y₂O₃, REO,        ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex metal oxides        thereof), wherein the amorphous material contains not more than        10 (in some embodiments preferably, less than 5 or even zero)        percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂,        TeO₂, and V₂O₅, based on the total weight of the amorphous        material of each particle; and    -   grading the abrasive particles comprising the glass-ceramic to        provide a plurality of abrasive particles having a specified        nominal grade, wherein at least a portion of the plurality of        abrasive particles is a plurality of the abrasive particles        comprising the glass-ceramic. In some embodiments, the glass and        glass-ceramic comprise 0 to 50, 0 to 25, or even 0 to 10 percent        by weight of the metal oxide other than Al₂O₃ (e.g., Y₂O₃, REO,        ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex metal oxides        thereof), and/or 0 to 50, 0 to 25, or even 0 to 10 percent by        weight of at least one of ZrO₂ or HfO₂, based on the total        weight of the glass and glass-ceramic, respectively.

In another aspect, the present invention provides a method for makingabrasive particles, the method comprising:

-   -   heat-treating amorphous material such that at least a portion of        the amorphous material is converted to a glass-ceramic, the        amorphous material comprising at least 35 (in some embodiments,        preferably at least 40, 45, 50, 55, 60, 65, or even at least 70)        percent by weight Al₂O₃, based on the total weight of the        amorphous material, and a metal oxide other than Al₂O₃ (e.g.,        Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex        metal oxides thereof), wherein the amorphous material contains        not more than 10 (in some embodiments preferably, less than 5 or        even zero) percent by weight collectively As₂O₃, B₂O₃, GeO₂,        P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of the        amorphous material;    -   crushing the glass-ceramic to provide abrasive particles        comprising the glass-ceramic; and    -   grading the abrasive particles comprising the glass-ceramic to        provide a plurality of abrasive particles having a specified        nominal grade, wherein at least a portion of the plurality of        abrasive particles is a plurality of the abrasive particles        comprising the glass-ceramic. In some embodiments, the glass and        glass-ceramic comprise 0 to 50, 0 to 25, or even 0 to 10 percent        by weight of the metal oxide other than Al₂O₃ (e.g., Y₂O₃, REO,        ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex metal oxides        thereof), and/or 0 to 50, 0 to 25, or even 0 to 10 percent by        weight of at least one of ZrO₂ or HfO₂, based on the total        weight of the glass and glass-ceramic, respectively.

In another aspect, the present invention provides a method for makingabrasive particles, the method comprising:

-   -   heat-treating ceramic comprising an amorphous material such that        at least a portion of the amorphous material is converted to a        glass-ceramic, the amorphous material comprising at least 35 (in        some embodiments, preferably at least 40, 45, 50, 55, 60, 65, or        even at least 70) percent by weight Al₂O₃, based on the total        weight of the amorphous material, and a metal oxide other than        Al₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO,        and complex metal oxides thereof), wherein the amorphous        material contains not more than 10 (in some embodiments        preferably, less than 5 or even zero) percent by weight        collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅,        based on the total weight of the amorphous material;    -   crushing the glass-ceramic to provide abrasive particles        comprising the glass-ceramic; and    -   grading the abrasive particles comprising the glass-ceramic to        provide a plurality of abrasive particles having a specified        nominal grade, wherein at least a portion of the plurality of        abrasive particles is a plurality of the abrasive particles        comprising the glass-ceramic. In some embodiments, the glass and        glass-ceramic comprise 0 to 50, 0 to 25, or even 0 to 10 percent        by weight of the metal oxide other than Al₂O₃ (e.g., Y₂O₃, REO,        ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex metal oxides        thereof), and/or 0 to 50, 0 to 25, or even 0 to 10 percent by        weight of at least one of ZrO₂ or HfO₂, based on the total        weight of the glass and glass-ceramic, respectively.

In another aspect, the present invention provides a method for makingceramic, the method comprising:

-   -   combining (a) glass particles, the glass comprising at least 35        (in some embodiments, preferably at least 40, 45, 50, 55, 60,        65, or even at least 70) percent by weight Al₂O₃, based on the        total weight of the glass, and a metal oxide other than Al₂O₃        (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and        complex metal oxides thereof), wherein the glass contains not        more than 10 (in some embodiments preferably, less than 5 or        even zero) percent by weight collectively As₂O₃, B₂O₃, GeO₂,        P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of the        glass, and (b) refractory particles (e.g., metal oxide        particles, boride particles, carbide particles, nitride        particles, diamond particles, metallic particles, glass        particles, and combinations thereof) relative to the glass        particles, the glass having a T_(g);    -   heating the glass particles above the T_(g) such that the glass        particles coalesce; and    -   cooling the glass to provide the ceramic. In some embodiments,        if the metal oxide other than Al₂O₃ is CaO, then the glass        particles and ceramic further comprises at least one distinct        crystalline phase of a metal oxide other than CaO. In some        embodiments, if the metal oxide other than Al₂O₃ is ZrO₂, then        the glass particles and ceramic further comprises at least one        distinct crystalline phase of a metal oxide other than ZrO₂. In        some embodiments, if the metal oxide other than Al₂O₃ is CaO or        ZrO₂, then the glass particles and ceramic further comprises at        least one distinct crystalline phase of a metal oxide other than        CaO or ZrO₂. In some embodiments, the glass and ceramic comprise        0 to 50, 0 to 25, or even 0 to 10 percent by weight of the metal        oxide other than Al₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃,        MgO, NiO, CuO, and complex metal oxides thereof), and/or 0 to        50, 0 to 25, or even 0 to 10 percent by weight of at least one        of ZrO₂ or HfO₂, based on the total weight of the glass and        ceramic, respectively.

In another aspect, the present invention provides a method for makingglass-ceramic, the method comprising:

-   -   combining (a) glass particles, the glass comprising at least 35        (in some embodiments, preferably at least 40, 45, 50, 55, 60,        65, or even at least 70) percent by weight Al₂O₃, based on the        total weight of the glass, and metal oxide other than Al₂O₃        (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and        complex metal oxides thereof), wherein the glass contains not        more than 10 (in some embodiments preferably, less than 5 or        even zero) percent by weight collectively As₂O₃, B₂O₃, GeO₂,        P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of the        glass, and (b) refractory particles (e.g., metal oxide        particles, boride particles, carbide particles, nitride        particles, diamond particles, metallic particles, glass        particles, and combinations thereof) relative to the glass        particles, the glass having a T_(g);    -   heating the glass particles above the T_(g) such that the glass        particles coalesce;    -   cooling the glass to provide ceramic comprising glass; and    -   heat-treating the ceramic such that at least a portion of the        glass is converted to a glass-ceramic. In some embodiments, if        the metal oxide other than Al₂O₃ is CaO, then the glass further        comprises a metal oxide other than Al₂O₃ or CaO at least a        portion of which forms a distinct crystalline phase when the        glass is crystallized, and the glass-ceramic further comprises        at least one distinct crystalline phase of a metal oxide other        than CaO. In some embodiments, if the metal oxide other than        Al₂O₃ is ZrO₂, then the glass further comprises a metal oxide        other than Al₂O₃ or ZrO₂ at least a portion of which forms a        distinct crystalline phase when the glass is crystallized, and        the glass-ceramic further comprises at least one distinct        crystalline phase of a metal oxide other than ZrO₂. In some        embodiments, if the metal oxide other than Al₂O₃ is CaO or ZrO₂,        then the glass further comprises a metal oxide other than Al₂O₃,        CaO, or ZrO₂ at least a portion of which forms a distinct        crystalline phase when the glass is crystallized, and the        glass-ceramic further comprises at least one distinct        crystalline phase of a metal oxide other than CaO or ZrO₂. In        some embodiments, the glass, ceramic, and glass-ceramic comprise        0 to 50, 0 to 25, or even 0 to 10 percent by weight of the metal        oxide other than Al₂O₃ (e.g., Y₂O₃, REO, ZrO₂, TiO₂, CaO, Cr₂O₃,        MgO, NiO, CuO, and complex metal oxides thereof), and/or 0 to        50, 0 to 25, or even 0 to 10 percent by weight of at least one        of ZrO₂ or HfO₂, based on the total weight of the glass,        ceramic, and glass-ceramic, respectively.

In this application:

“amorphous material” refers to material derived from a melt and/or avapor phase that lacks any long range crystal structure as determined byX-ray diffraction and/or has an exothermic peak corresponding to thecrystallization of the amorphous material as determined by a DTA(differential thermal analysis) as determined by the test describedherein entitled “Differential Thermal Analysis”;

“ceramic” includes amorphous material, glass, crystalline ceramic,glass-ceramic, and combinations thereof;

“complex metal oxide” refers to a metal oxide comprising two or moredifferent metal elements and oxygen (e.g., CeAl₁₁O₁₈, Dy₃Al₅O₁₂,MgAl₂O₄, and Y₃Al₅O₁₂);

“complex Al₂O₃•metal oxide” refers to a complex metal oxide comprising,on a theoretical oxide basis, Al₂O₃ and one or more metal elements otherthan Al (e.g., CeAl₁₁O₁₈, Dy₃Al₅O₁₂, MgAl₂O₄, and Y₃Al₅O₁₂);

“complex Al₂O₃.Y₂O₃” refers to a complex metal oxide comprising, on atheoretical oxide basis, Al₂O₃ and Y₂O₃ (e.g., Y₃Al₅O₁₂);

“complex Al₂O₃.REO” refers to a complex metal oxide comprising, on atheoretical oxide basis, Al₂O₃ and rare earth oxide (e.g., CeAl₁₁O₁₈ andDy₃Al₅O₁₂);

“glass” refers to amorphous material exhibiting a glass transitiontemperature;

“glass-ceramic” refers to ceramics comprising crystals formed byheat-treating amorphous material;

“T_(g)” refers to the glass transition temperature as determined in bythe test described herein entitled “Differential Thermal Analysis”;

“T_(x)” refers to the crystallization temperature as determined in bythe test described herein entitled “Differential Thermal Analysis”;

“rare earth oxides” refers to cerium oxide (e.g., CeO₂), dysprosiumoxide (e.g., Dy₂O₃), erbium oxide (e.g., Er₂O₃), europium oxide (e.g.,Eu₂O₃), gadolinium (e.g., Gd₂O₃), holmium oxide (e.g., Ho₂O₃), lanthanumoxide (e.g., La₂O₃), lutetium oxide (e.g., Lu₂O₃), neodymium oxide(e.g., Nd₂O₃), praseodymium oxide (e.g., Pr₆O₁₁), samarium oxide (e.g.,Sm₂O₃), terbium (e.g., Tb₂O₃), thorium oxide (e.g., Th₄O₇), thulium(e.g., Tm₂O₃), and ytterbium oxide (e.g., Yb₂O₃), and combinationsthereof; and

“REO” refers to rare earth oxide(s).

Further, it is understood herein that unless it is stated that a metaloxide (e.g., Al₂O₃, complex Al₂O₃-metal oxide, etc.) is crystalline, forexample, in a glass-ceramic, it may be amorphous, crystalline, orportions amorphous and portions crystalline. For example if aglass-ceramic comprises Al₂O₃ and ZrO₂, the Al₂O₃ and ZrO₂ may each bein an amorphous state, crystalline state, or portions in an amorphousstate and portions in a crystalline state, or even as a reaction productwith another metal oxide(s) (e.g., unless it is stated that, forexample, Al₂O₃ is present as crystalline Al₂O₃ or a specific crystallinephase of Al₂O₃ (e.g., alpha Al₂O₃), it may be present as crystallineAl₂O₃ and/or as part of one or more crystalline complex Al₂O₃•metaloxides.

Further, it is understood that glass-ceramics formed by heatingamorphous material not exhibiting a T_(g) may not actually compriseglass, but rather may comprise the crystals and amorphous material thatdoes not exhibiting a T_(g).

Amorphous materials and glass-ceramics according to the presentinvention can be made, formed as, or converted into particles (e.g.,glass beads (e.g., beads having diameters of at least 1 micrometers, 5micrometers, 10 micrometers, 25 micrometers, 50 micrometers, 100micrometers, 150 micrometers, 250 micrometers, 500 micrometers, 750micrometers, 1 mm, 5 mm, or even at least 10 mm)), articles (e.g.,plates), fibers, particles, and coatings (e.g., thin coatings).Amorphous materials and/or glass-ceramic particles and fibers areuseful, for example, as thermal insulation, filler, or reinforcingmaterial in composites (e.g., ceramic, metal, or polymeric matrixcomposites). The thin coatings can be useful, for example, as protectivecoatings in applications involving wear, as well as for thermalmanagement. Examples of articles according of the present inventioninclude kitchenware (e.g., plates), dental brackets, and reinforcingfibers, cutting tool inserts, abrasive materials, and structuralcomponents of gas engines, (e.g., valves and bearings). Other articlesinclude those having a protective coating of ceramic on the outersurface of a body or other substrate.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a fragmentary cross-sectional schematic view of a coatedabrasive article including abrasive particles according to the presentinvention;

FIG. 2 is a perspective view of a bonded abrasive article includingabrasive particles according to the present invention; and

FIG. 3 is an enlarged schematic view of a nonwoven abrasive articleincluding abrasive particles according to the present invention;

FIG. 4 is a DTA of the material prepared in Example 1;

FIG. 5 is a Scanning Electron Micrograph (SEM) of fractured surface ofmaterial prepared in Example 22;

FIG. 6 is a Scanning Electron Micrograph (SEM) of fractured surface ofmaterial prepared in Example 24;

FIG. 7 is a Scanning Electron Micrograph (SEM) of fractured surface ofmaterial prepared in Example 30;

FIG. 8 is a Scanning Electron Micrograph (SEM) of fractured surface ofmaterial prepared in Example 30;

FIG. 9 is a Scanning Electron Micrograph (SEM) of fractured surface ofmaterial prepared in Example 31;

FIG. 10 is a back scattered electron micrograph of the material preparedin Example 32;

FIG. 11 is a DTA curve of Example 35 material;

FIGS. 12–15 are DTA curves of materials of Examples 36–39, respectively;and

FIG. 16 is an optical photomicrograph of a sectioned bar (2-mm thick) ofthe hot-pressed material of Example 47;

FIG. 17 is a scanning electron microscope (SEM) photomicrograph of apolished section of heat-treated Example 47 material;

FIG. 18 is a DTA trace for Example 47 material; and

FIG. 19 is an SEM photomicrograph of a polished section of Example 65material.

DETAILED DESCRIPTION

Some embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising glass-ceramics, amorphous materials (including glasses) formaking the glass-ceramics, abrasive particles, etc. include thosecomprising Al₂O₃, and at least one other metal oxide (e.g., REO and; REOand at least one of ZrO₂ or HfO₂), wherein at least 80 (85, 90, 95, 97,98, 99, or even 100) percent by weight of the amorphous material,glass-ceramic, etc., as applicable, collectively comprises the comprisesthe Al₂O₃, and at least one other metal oxide, based on the total weightof the amorphous material, glass-ceramic, etc., as applicable.

Amorphous materials (e.g., glasses), ceramics comprising the amorphousmaterial, particles comprising the amorphous material, etc. can be made,for example, by heating (including in a flame) the appropriate metaloxide sources to form a melt, desirably a homogenous melt, and thenrapidly cooling the melt to provide amorphous material. Embodiments ofamorphous materials can be made, for example, by melting the metal oxidesources in any suitable furnace (e.g., an inductive heated furnace, agas-fired furnace, or an electrical furnace), or, for example, in aplasma. The resulting melt is cooled (e.g., discharging the melt into acooling media (e.g., high velocity air jets, liquids, metal plates(including chilled metal plates), metal rolls (including chilled metalrolls), metal balls (including chilled metal balls), and the like)).

Embodiments of amorphous material can be made utilizing flame fusion asdisclosed, for example, in U.S. Pat. No. 6,254,981 (Castle), thedisclosure of which is incorporated herein by reference. In this method,the metal oxide sources materials are fed (e.g., in the form ofparticles, sometimes referred to as “feed particles”) directly into aburner (e.g., a methane-air burner, an acetylene-oxygen burner, ahydrogen-oxygen burner, and like), and then quenched, for example, inwater, cooling oil, air, or the like. Feed particles can be formed, forexample, by grinding, agglomerating (e.g., spray-drying), melting, orsintering the metal oxide sources. The size of feed particles fed intothe flame generally determine the size of the resulting amorphousmaterial comprising particles.

Embodiments of amorphous materials can also be obtained by othertechniques, such as: laser spin melt with free fall cooling, Taylor wiretechnique, plasmatron technique, hammer and anvil technique, centrifugalquenching, air gun splat cooling, single roller and twin rollerquenching, roller-plate quenching and pendant drop melt extraction (see,e.g., Rapid Solidification of Ceramics, Brockway et al., Metals AndCeramics Information Center, A Department of Defense InformationAnalysis Center, Columbus, Ohio, January, 1984, the disclosure of whichis incorporated here as a reference). Embodiments of amorphous materialsmay also be obtained by other techniques, such as: thermal (includingflame or laser or plasma-assisted) pyrolysis of suitable precursors,physical vapor synthesis (PVS) of metal precursors and mechanochemicalprocessing.

Useful amorphous material formulations include those at or near aeutectic composition(s) (e.g., binary and ternary eutecticcompositions). In addition to compositions disclosed herein, othercompositions, including quaternary and other higher order eutecticcompositions, may be apparent to those skilled in the art afterreviewing the present disclosure.

Typically, amorphous materials, and the glass-ceramics according to thepresent invention made there from, have x, y, and z dimensions eachperpendicular to each other, and wherein each of the x, y, and zdimensions is at least 25 micrometers. In some embodiments, the x, y,and z dimensions is at least 30 micrometers, 35 micrometers, 40micrometers, 45 micrometers, 50 micrometers, 75 micrometers, 100micrometers, 150 micrometers, 200 micrometers, 250 micrometers, 500micrometers, 1000 micrometers, 2000 micrometers, 2500 micrometers, 1 mm,5 mm, or even at least 10 mm.

Sources, including commercial sources, of (on a theoretical oxide basis)Al₂O₃ include bauxite (including both natural occurring bauxite andsynthetically produced bauxite), calcined bauxite, hydrated aluminas(e.g., boehmite, and gibbsite), aluminum, Bayer process alumina,aluminum ore, gamma alumina, alpha alumina, aluminum salts, aluminumnitrates, and combinations thereof. The Al₂O₃ source may contain, oronly provide, Al₂O₃. Alternatively, the Al₂O₃ source may contain, orprovide Al₂O₃, as well as one or more metal oxides other than Al₂O₃(including materials of or containing complex Al₂O₃•metal oxides (e.g.,Dy₃Al₅O₁₂, Y₃Al₅O₁₂, CeAl₁₁O₁₈, etc.)).

Sources, including commercial sources, of rare earth oxides include rareearth oxide powders, rare earth metals, rare earth-containing ores(e.g., bastnasite and monazite), rare earth salts, rare earth nitrates,and rare earth carbonates. The rare earth oxide(s) source may contain,or only provide, rare earth oxide(s). Alternatively, the rare earthoxide(s) source may contain, or provide rare earth oxide(s), as well asone or more metal oxides other than rare earth oxide(s) (includingmaterials of or containing complex rare earth oxide•other metal oxides(e.g., Dy₃Al₅O₁₂, CeAl₁₁O₁₈, etc.)).

Sources, including commercial sources, of (on a theoretical oxide basis)Y₂O₃ include yttrium oxide powders, yttrium, yttrium-containing ores,and yttrium salts (e.g., yttrium carbonates, nitrates, chlorides,hydroxides, and combinations thereof). The Y₂O₃ source may contain, oronly provide, Y₂O₃. Alternatively, the Y₂O₃ source may contain, orprovide Y₂O₃, as well as one or more metal oxides other than Y₂O₃(including materials of or containing complex Y₂O₃•metal oxides (e.g.,Y₃Al₅O₁₂)).

Sources, including commercial sources, of (on a theoretical oxide basis)ZrO₂ include zirconium oxide powders, zircon sand, zirconium,zirconium-containing ores, and zirconium salts (e.g., zirconiumcarbonates, acetates, nitrates, chlorides, hydroxides, and combinationsthereof). In addition, or alternatively, the ZrO₂ source may contain, orprovide ZrO₂, as well as other metal oxides such as hafnia. Sources,including commercial sources, of (on a theoretical oxide basis) HfO₂include hafnium oxide powders, hafnium, hafnium-containing ores, andhafnium salts. In addition, or alternatively, the HfO₂ source maycontain, or provide HfO₂, as well as other metal oxides such as ZrO₂.

Other useful metal oxide may also include, on a theoretical oxide basis,BaO, CaO, Cr₂O₃, CoO, Fe₂O₃, GeO₂, Li₂O, MgO, MnO, NiO, Na₂O, Sc₂O₃,SrO, TiO₂, ZnO, and combinations thereof. Sources, including commercialsources, include the oxides themselves, complex oxides, ores,carbonates, acetates, nitrates, chlorides, hydroxides, etc. These metaloxides are added to modify a physical property of the resulting abrasiveparticles and/or improve processing. These metal oxides are typicallyare added anywhere from 0 to 50% by weight, in some embodimentspreferably 0 to 25% by weight and more preferably 0 to 50% by weight ofthe glass-ceramic depending, for example, upon the desired property.

In some embodiments, it may be advantageous for at least a portion of ametal oxide source (in some embodiments, preferably, 10, 15, 20, 25, 30,35, 40, 45, or even at least 50 percent by weight) to be obtained byadding particulate, metallic material comprising at least one of a metal(e.g., Al, Ca, Cu, Cr, Fe, Li, Mg, Ni, Ag, Ti, Zr, and combinationsthereof), M, that has a negative enthalpy of oxide formation or an alloythereof to the melt, or otherwise metal them with the other rawmaterials. Although not wanting to be bound by theory, it is believedthat the heat resulting from the exothermic reaction associated with theoxidation of the metal is beneficial in the formation of a homogeneousmelt and resulting amorphous material. For example, it is believed thatthe additional heat generated by the oxidation reaction within the rawmaterial eliminates or minimizes insufficient heat transfer, and hencefacilitates formation and homogeneity of the melt, particularly whenforming amorphous particles with x, y, and z dimensions over 150micrometers. It is also believed that the availability of the additionalheat aids in driving various chemical reactions and physical processes(e.g., densification, and spherodization) to completion. Further, it isbelieved for some embodiments, the presence of the additional heatgenerated by the oxidation reaction actually enables the formation of amelt, which otherwise is difficult or otherwise not practical due tohigh melting point of the materials. Further, the presence of theadditional heat generated by the oxidation reaction actually enables theformation of amorphous material that otherwise could not be made, orcould not be made in the desired size range. Another advantage of theinvention include, in forming the amorphous materials, that many of thechemical and physical processes such as melting, densification andspherodizing can be achieved in a short time, so that very high quenchrates be can achieved. For additional details, see copending applicationhaving U.S. Ser. No. 10/211,639, filed the same date as the instantapplication, the disclosure of which is incorporated herein byreference.

The particular selection of metal oxide sources and other additives formaking ceramics according to the present invention typically takes intoaccount, for example, the desired composition and microstructure of theresulting ceramics, the desired degree of crystallinity, if any, thedesired physical properties (e.g., hardness or toughness) of theresulting ceramics, avoiding or minimizing the presence of undesirableimpurities, the desired characteristics of the resulting ceramics,and/or the particular process (including equipment and any purificationof the raw materials before and/or during fusion and/or solidification)being used to prepare the ceramics.

In some instances, it may be preferred to incorporate limited amounts ofmetal oxides selected from the group consisting of: Na₂O, P₂O₅, SiO₂,TeO₂, V₂O₃, and combinations thereof. Sources, including commercialsources, include the oxides themselves, complex oxides, ores,carbonates, acetates, nitrates, chlorides, hydroxides, etc. These metaloxides may be added, for example, to modify a physical property of theresulting abrasive particles and/or improve processing. These metaloxides when used are typically are added from greater than 0 to 20% byweight, preferably greater than 0 to 5% by weight and more preferablygreater than 0 to 2% by weight of the glass-ceramic depending, forexample, upon the desired property.

The addition of certain metal oxides may alter the properties and/orcrystalline structure or microstructure of a glass-ceramic according tothe present invention, as well as the processing of the raw materialsand intermediates in making the glass-ceramic. For example, oxideadditions such as MgO, CaO, Li₂O, and Na₂O have been observed to alterboth the T_(g) (for a glass) and T_(x) (wherein T_(x) is thecrystallization temperature) of amorphous material. Although not wishingto be bound by theory, it is believed that such additions influenceglass formation. Further, for example, such oxide additions may decreasethe melting temperature of the overall system (i.e., drive the systemtoward lower melting eutectic), and ease of amorphousmaterial-formation. Complex eutectics in multi component systems(quaternary, etc.) may result in better amorphous material-formingability. The viscosity of the liquid melt and viscosity of the glass inits “working” range may also be affected by the addition of certainmetal oxides such as MgO, CaO, Li₂O, and Na₂O. It is also within thescope of the present invention to incorporate at least one of halogens(e.g., fluorine and chlorine), or chalcogenides (e.g., sulfides,selenides, and tellurides) into the amorphous materials, and theglass-ceramics made there from.

Crystallization of the amorphous material and ceramic comprising theamorphous material may also be affected by the additions of certainmaterials. For example, certain metals, metal oxides (e.g., titanatesand zirconates), and fluorides, for example, may act as nucleationagents resulting in beneficial heterogeneous nucleation of crystals.Also, addition of some oxides may change nature of metastable phasesdevitrifying from the amorphous material upon reheating. In anotheraspect, for ceramics comprising crystalline ZrO₂, it may be desirable toadd metal oxides (e.g., Y₂O₃, TiO₂, CaO, and MgO) that are known tostabilize tetragonal/cubic form of ZrO₂.

The metal oxide sources and other additives can be in any form suitableto the process and equipment being used to make the glass-ceramicsaccording to the present invention. The raw materials can be melted andquenched using techniques and equipment known in the art for makingoxide amorphous materials and amorphous metals. Desirable cooling ratesinclude those of 50 K/s and greater. Cooling techniques known in the artinclude roll-chilling. Roll-chilling can be carried out, for example, bymelting the metal oxide sources at a temperature typically 20–200° C.higher than the melting point, and cooling/quenching the melt byspraying it under high pressure (e.g., using a gas such as air, argon,nitrogen or the like) onto a high-speed rotary roll(s). Typically, therolls are made of metal and are water cooled. Metal book molds may alsobe useful for cooling/quenching the melt.

Other techniques for forming melts, cooling/quenching melts, and/orotherwise forming amorphous material include vapor phase quenching,melt-extraction, plasma spraying, and gas or centrifugal atomization.Vapor phase quenching can be carried out, for example, by sputtering,wherein the metal alloys or metal oxide sources are formed into asputtering target(s) which are used. The target is fixed at apredetermined position in a sputtering apparatus, and a substrate(s) tobe coated is placed at a position opposing the target(s). Typicalpressures of 10⁻³ torr of oxygen gas and Ar gas, discharge is generatedbetween the target(s) and a substrate(s), and Ar or oxygen ions collideagainst the target to start reaction sputtering, thereby depositing afilm of composition on the substrate. For additional details regardingplasma spraying, see, for example, copending application having U.S.Ser. No. 10/211,640, filed the same date as the instant application, thedisclosure of which is incorporated herein by reference.

Gas atomization involves melting feed particles to convert them to melt.A thin stream of such melt is atomized through contact with a disruptiveair jet (i.e., the stream is divided into fine droplets). The resultingsubstantially discrete, generally ellipsoidal amorphous materialcomprising particles (e.g., beads) are then recovered. Examples of beadsizes include those having a diameter in a range of about 5 micrometersto about 3 mm. Melt-extraction can be carried out, for example, asdisclosed in U.S. Pat. No. 5,605,870 (Strom-Olsen et al.), thedisclosure of which is incorporated herein by reference. Containerlessglass forming techniques utilizing laser beam heating as disclosed, forexample, in PCT application having Publication No. WO 01/27046 A1,published Apr. 4, 2001, the disclosure of which is incorporated hereinby reference, may also be useful in making materials according to thepresent invention.

The cooling rate is believed to affect the properties of the quenchedamorphous material. For instance, glass transition temperature, densityand other properties of glass typically change with cooling rates.

Typically, it is preferred that the bulk material comprises at least 50,60, 75, 80, 85, 90, 95, 98, 99, or even 100 percent by weight of theamorphous material.

Rapid cooling may also be conducted under controlled atmospheres, suchas a reducing, neutral, or oxidizing environment to maintain and/orinfluence the desired oxidation states, etc. during cooling. Theatmosphere can also influence amorphous material formation byinfluencing crystallization kinetics from undercooled liquid. Forexample, larger undercooling of Al₂O₃ melts without crystallization hasbeen reported in argon atmosphere as compared to that in air.

The microstructure or phase composition (glassy/amorphous/crystalline)of a material can be determined in a number of ways. Various informationcan be obtained using optical microscopy, electron microscopy,differential thermal analysis (DTA), and x-ray diffraction (XRD), forexample.

Using optical microscopy, amorphous material is typically predominantlytransparent due to the lack of light scattering centers such as crystalboundaries, while crystalline material shows a crystalline structure andis opaque due to light scattering effects.

A percent amorphous yield can be calculated for beads using a −100+120mesh size fraction (i.e., the fraction collected between 150-micrometeropening size and 125-micrometer opening size screens). The measurementsare done in the following manner. A single layer of beads is spread outupon a glass slide. The beads are observed using an optical microscope.Using the crosshairs in the optical microscope eyepiece as a guide,beads that lay along a straight line are counted either amorphous orcrystalline depending on their optical clarity. A total of 500 beads arecounted and a percent amorphous yield is determined by the amount ofamorphous beads divided by total beads counted.

Using DTA, the material is classified as amorphous if the correspondingDTA trace of the material contains an exothermic crystallization event(T_(x)). If the same trace also contains an endothermic event (T_(g)) ata temperature lower than T_(x) it is considered to consist of a glassphase. If the DTA trace of the material contains no such events, it isconsidered to contain crystalline phases.

Differential thermal analysis (DTA) can be conducted using the followingmethod. DTA runs can be made (using an instrument such as that obtainedfrom Netzsch Instruments, Selb, Germany under the trade designation“NETZSCH STA 409 DTA/TGA”) using a −140+170 mesh size fraction (i.e.,the fraction collected between 105-micrometer opening size and90-micrometer opening size screens). An amount of each screened sample(typically about 400 milligrams (mg)) is placed in a 100-microliterAl₂O₃ sample holder. Each sample is heated in static air at a rate of10° C./minute from room temperature (about 25° C.) to 1100° C.

Using powder x-ray diffraction, XRD, (using an x-ray diffractometer suchas that obtained under the trade designation “PHILLIPS XRG 3100” fromPhillips, Mahwah, N.J., with copper K α1 radiation of 1.54050 Angstrom)the phases present in a material can be determined by comparing thepeaks present in the XRD trace of the crystallized material to XRDpatterns of crystalline phases provided in JCPDS (Joint Committee onPowder Diffraction Standards) databases, published by InternationalCenter for Diffraction Data. Furthermore, an XRD can be usedqualitatively to determine types of phases. The presence of a broaddiffused intensity peak is taken as an indication of the amorphousnature of a material. The existence of both a broad peak andwell-defined peaks is taken as an indication of existence of crystallinematter within an amorphous matrix.

The initially formed amorphous material or ceramic (including glassprior to crystallization) may be larger in size than that desired. Theamorphous material or ceramic can be converted into smaller pieces usingcrushing and/or comminuting techniques known in the art, including rollcrushing, canary milling, jaw crushing, hammer milling, ball milling,jet milling, impact crushing, and the like. In some instances, it isdesired to have two or multiple crushing steps. For example, after theceramic is formed (solidified), it may be in the form of larger thandesired. The first crushing step may involve crushing these relativelylarge masses or “chunks” to form smaller pieces. This crushing of thesechunks may be accomplished with a hammer mill, impact crusher or jawcrusher. These smaller pieces may then be subsequently crushed toproduce the desired particle size distribution. In order to produce thedesired particle size distribution (sometimes referred to as grit sizeor grade), it may be necessary to perform multiple crushing steps. Ingeneral the crushing conditions are optimized to achieve the desiredparticle shape(s) and particle size distribution. Resulting particlesthat are of the desired size may be recrushed if they are too large, or“recycled” and used as a raw material for re-melting if they are toosmall.

The shape of the ceramic (including glass prior to crystallization) maydepend, for example, on the composition and/or microstructure of theceramic, the geometry in which it was cooled, and the manner in whichthe ceramic is crushed (i.e., the crushing technique used). In general,where a “blocky” shape is preferred, more energy may be employed toachieve this shape. Conversely, where a “sharp” shape is preferred, lessenergy may be employed to achieve this shape. The crushing technique mayalso be changed to achieve different desired shapes. For some particlesan average aspect ratio ranging from 1:1 to 5:1 is typically desired,and in some embodiments 1.25:1 to 3:1, or even 1.5:1 to 2.5:1.

It is also within the scope of the present invention, for example, todirectly form ceramic (including glass prior to crystallization) may indesired shapes. For example, ceramic (including glass prior tocrystallization) may be formed (including molded) by pouring or formingthe melt into a mold.

It is also within the scope of the present invention, for example, tofabricate the ceramic (including glass prior to crystallization) bycoalescing. This coalescing step in essence forms a larger sized bodyfrom two or more smaller particles. For example, amorphous materialcomprising particles (obtained, for example, by crushing) (includingbeads and microspheres), fibers, etc. may formed into a larger particlesize. For example, ceramic (including glass prior to crystallization),may also be provided by heating, for example, particles comprising theamorphous material, and/or fibers, etc. above the T_(g) such that theparticles, etc. coalesce to form a shape and cooling the coalescedshape. The temperature and pressure used for coalescing may depend, forexample, upon composition of the amorphous material and the desireddensity of the resulting material. The temperature should below glasscrystallization temperature, and for glasses, greater than the glasstransition temperature. In certain embodiments, the heating is conductedat at least one temperature in a range of about 850° C. to about 1100°C. (in some embodiments, preferably 900° C. to 1000° C.). Typically, theamorphous material is under pressure (e.g., greater than zero to 1 GPaor more) during coalescence to aid the coalescence of the amorphousmaterial. In one embodiment, a charge of the particles, etc. is placedinto a die and hot-pressing is performed at temperatures above glasstransition where viscous flow of glass leads to coalescence into arelatively large part. Examples of typical coalescing techniques includehot pressing, hot isostatic pressure, hot extrusion and the like.Typically, it is generally preferred to cool the resulting coalescedbody before further heat treatment. After heat treatment if so desired,the coalesced body may be crushed to smaller particle sizes or a desiredparticle size distribution.

It is also within the scope of the present invention to conductadditional heat-treatment to further improve desirable properties of thematerial. For example, hot-isostatic pressing may be conducted (e.g., attemperatures from about 900° C. to about 1400° C.) to remove residualporosity, increasing the density of the material. Optionally, theresulting, coalesced article can be heat-treated to provideglass-ceramic, crystalline ceramic, or ceramic otherwise comprisingcrystalline ceramic.

Coalescence of the amorphous material and/or glass-ceramic (e.g.,particles) may also be accomplished by a variety of methods, includingpressureless or pressure sintering (e.g., sintering, plasma assistedsintering, hot pressing, HIPing, hot forging, hot extrusion, etc.).

Heat-treatment can be carried out in any of a variety of ways, includingthose known in the art for heat-treating glass to provideglass-ceramics. For example, heat-treatment can be conducted in batches,for example, using resistive, inductively or gas heated furnaces.Alternatively, for example, heat-treatment can be conductedcontinuously, for example, using rotary kilns. In the case of a rotarykiln, the material is fed directly into a kiln operating at the elevatedtemperature. The time at the elevated temperature may range from a fewseconds (in some embodiments even less than 5 seconds) to a few minutesto several hours. The temperature may range anywhere from 900° C. to1600° C., typically between 1200° C. to 1500° C. It is also within thescope of the present invention to perform some of the heat-treatment inbatches (e.g., for the nucleation step) and another continuously (e.g.,for the crystal growth step and to achieve the desired density). For thenucleation step, the temperature typically ranges between about 900° C.to about 1100° C., in some embodiments, preferably in a range from about925° C. to about 1050° C. Likewise for the density step, the temperaturetypically is in a range from about 1100° C. to about 1600° C., in someembodiments, preferably in a range from about 1200° C. to about 1500° C.This heat treatment may occur, for example, by feeding the materialdirectly into a furnace at the elevated temperature. Alternatively, forexample, the material may be feed into a furnace at a much lowertemperature (e.g., room temperature) and then heated to desiredtemperature at a predetermined heating rate. It is within the scope ofthe present invention to conduct heat-treatment in an atmosphere otherthan air. In some cases it might be even desirable to heat-treat in areducing atmosphere(s). Also, for, example, it may be desirable toheat-treat under gas pressure as in, for example, hot-isostatic press,or in gas pressure furnace. It is within the scope of the presentinvention to convert (e.g., crush) the resulting article or heat-treatedarticle to provide particles (e.g., abrasive particles).

The amorphous material is heat-treated to at least partially crystallizethe amorphous material to provide glass-ceramic. The heat-treatment ofcertain glasses to form glass-ceramics is well known in the art. Theheating conditions to nucleate and grow glass-ceramics are known for avariety of glasses. Alternatively, one skilled in the art can determinethe appropriate conditions from a Time-Temperature-Transformation (TTT)study of the glass using techniques known in the art. One skilled in theart, after reading the disclosure of the present invention should beable to provide TTT curves for glasses according to the presentinvention, determine the appropriate nucleation and/or crystal growthconditions to provide glass-ceramics according to the present invention.

Typically, glass-ceramics are stronger than the amorphous materials fromwhich they are formed. Hence, the strength of the material may beadjusted, for example, by the degree to which the amorphous material isconverted to crystalline ceramic phase(s). Alternatively, or inaddition, the strength of the material may also be affected, forexample, by the number of nucleation sites created, which may in turn beused to affect the number, and in turn the size of the crystals of thecrystalline phase(s). For additional details regarding formingglass-ceramics, see, for example, Glass-Ceramics, P. W. McMillan,Academic Press, Inc., 2^(nd) edition, 1979, the disclosure of which isincorporated herein by reference.

For example, during heat-treatment of some exemplary amorphous materialsfor making glass-ceramics according to present invention, formation ofphases such as La₂Zr₂O₇, and, if ZrO₂ is present, cubic/tetragonal ZrO₂,in some cases monoclinic ZrO₂, have been observed at temperatures aboveabout 900° C. Although not wanting to be bound by theory, it is believedthat zirconia-related phases are the first phases to nucleate from theamorphous material. Formation of Al₂O₃, ReAlO₃ (wherein Re is at leastone rare earth cation), ReAl₁₁O₁₈, Re₃Al₅O₁₂, Y₃Al₅O₁₂, etc. phases arebelieved to generally occur at temperatures above about 925° C.Typically, crystallite size during this nucleation step is on order ofnanometers. For example, crystals as small as 10–15 nanometers have beenobserved. For at least some embodiments, heat-treatment at about 1300°C. for about 1 hour provides a full crystallization. In generally,heat-treatment times for each of the nucleation and crystal growth stepsmay range of a few seconds (in some embodiments even less than 5seconds) to several minutes to an hour or more.

The size of the resulting crystals can typically controlled at least inpart by the nucleation and/or crystallization times and/or temperatures.Although it is generally preferred to have small crystals (e.g., on theorder not greater than a micrometer, or even not greater than ananometer) glass-ceramics according to the present invention may be madewith larger crystal sizes (e.g., at least 1–10 micrometers, at least10–25 micrometers, at least 50–100 micrometers, or even grater than 100micrometers). Although not wanting to be bound by theory, it isgenerally believed in the art that the finer the size of the crystals(for the same density), the higher the mechanical properties (e.g.,hardness and strength) of the ceramic.

Examples of crystalline phases which may be present in embodiments ofabrasive particles according to the present invention include: Al₂O₃(e.g., α-Al₂O₃), Y₂O₃, REO, HfO₂ ZrO₂ (e.g., cubic ZrO₂ and tetragonalZrO₂), BaO, CaO, Cr₂O₃, CoO, Fe₂O₃, GeO₂, Li₂O, MgO, MnO, NiO, Na₂O,P₂O₅, Sc₂O₃, SiO₂, SrO, TeO₂, TiO₂, V₂O₃, Y₂O₃, ZnO, “complex metaloxides” (including “complex Al₂O₃•metal oxide (e.g., complex Al₂O₃•REO(e.g., ReAlO₃ (e.g., GdAl O₃ LaAlO₃), ReAl₁₁O₁₈ (e.g., LaAl₁₁O₁₈,), andRe₃Al₅O₁₂ (e.g., Dy₃Al₅O₁₂)), complex Al₂O₃.Y₂O₃ (e.g., Y₃Al₅O₁₂), andcomplex ZrO₂•REO (e.g., Re₂Zr₂O₇ (e.g., La₂Zr₂O₇))), and combinationsthereof

It is also with in the scope of the present invention to substitute aportion of the yttrium and/or aluminum cations in a complex Al₂O₃•metaloxide (e.g., complex Al₂O₃.Y₂O₃ (e.g., yttrium aluminate exhibiting agarnet crystal structure)) with other cations. For example, a portion ofthe Al cations in a complex Al₂O₃.Y₂O₃ may be substituted with at leastone cation of an element selected from the group consisting of: Cr, Ti,Sc, Fe, Mg, Ca, Si, Co, and combinations thereof. For example, a portionof the Y cations in a complex Al₂O₃.Y₂O₃ may be substituted with atleast one cation of an element selected from the group consisting of:Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Th, Tm, Yb, Fe, Ti, Mn, V,Cr, Co, Ni, Cu, Mg, Ca, Sr, and combinations thereof. Similarly, it isalso with in the scope of the present invention to substitute a portionof the aluminum cations in alumina. For example, Cr, Ti, Sc, Fe, Mg, Ca,Si, and Co can substitute for aluminum in the alumina. The substitutionof cations as described above may affect the properties (e.g. hardness,toughness, strength, thermal conductivity, etc.) of the fused material.

It is also with in the scope of the present invention to substitute aportion of the rare earth and/or aluminum cations in a complexAl₂O₃•metal oxide (e.g., complex Al₂O₃•REO) with other cations. Forexample, a portion of the Al cations in a complex Al₂O₃•REO may besubstituted with at least one cation of an element selected from thegroup consisting of: Cr, Ti, Sc, Fe, Mg, Ca, Si, Co, and combinationsthereof. For example, a portion of the Y cations in a complex Al₂O₃•REOmay be substituted with at least one cation of an element selected fromthe group consisting of: Y, Fe, Ti, Mn, V, Cr, Co, Ni, Cu, Mg, Ca, Sr,and combinations thereof. Similarly, it is also with in the scope of thepresent invention to substitute a portion of the aluminum cations inalumina. For example, Cr, Ti, Sc, Fe, Mg, Ca, Si, and Co can substitutefor aluminum in the alumina. The substitution of cations as describedabove may affect the properties (e.g. hardness, toughness, strength,thermal conductivity, etc.) of the fused material.

The average crystal size can be determined by the line intercept methodaccording to the ASTM standard E 112-96 “Standard Test Methods forDetermining Average Grain Size”. The sample is mounted in mounting resin(such as that obtained under the trade designation “TRANSOPTIC POWDER”from Buehler, Lake Bluff, Ill.) typically in a cylinder of resin about2.5 cm in diameter and about 1.9 cm high. The mounted section isprepared using conventional polishing techniques using a polisher (suchas that obtained from Buehler, Lake Bluff, Ill. under the tradedesignation “ECOMET 3”). The sample is polished for about 3 minutes witha diamond wheel, followed by 5 minutes of polishing with each of 45, 30,15, 9, 3, and 1-micrometer slurries. The mounted and polished sample issputtered with a thin layer of gold-palladium and viewed using ascanning electron microscopy (such as the JEOL SEM Model JSM 840A). Atypical back-scattered electron (BSE) micrograph of the microstructurefound in the sample is used to determine the average crystal size asfollows. The number of crystals that intersect per unit length (N_(L))of a random straight line drawn across the micrograph are counted. Theaverage crystal size is determined from this number using the followingequation.

${{Average}\mspace{14mu}{Crystal}\mspace{14mu}{Size}} = \frac{1.5}{N_{L}M}$

Where N_(L) is the number of crystals intersected per unit length and Mis the magnification of the micrograph.

Some embodiments of the present invention include glass-ceramicscomprising alpha alumina having at least one of an average crystal sizenot greater than 150 nanometers.

Some embodiments of the present invention include glass-ceramicscomprising alpha alumina, wherein at least 90 (in some embodimentspreferably, 95, or even 100) percent by number of the alpha aluminapresent in such portion have crystal sizes not greater than 200nanometers.

Some embodiments of the present invention include glass-ceramicscomprising alpha Al₂O₃, crystalline ZrO₂, and a first complexAl₂O₃.Y₂O₃, and wherein at least one of the alpha Al₂O₃, the crystallineZrO₂, or the first complex Al₂O₃.Y₂O₃ has an average crystal size notgreater than 150 nanometers. In some embodiments preferably, theglass-ceramics further comprise a second, different complex Al₂O₃.Y₂O₃.In some embodiments preferably, the glass-ceramics further comprise acomplex Al₂O₃-REO.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃.Y₂O₃, a second, different complexAl₂O₃.Y₂O₃, and crystalline ZrO₂, and wherein for at least one of thefirst complex Al₂O₃.Y₂O₃, the second complex Al₂O₃.Y₂O₃, or thecrystalline ZrO₂, at least 90 (in some embodiments preferably, 95, oreven 100) percent by number of the crystal sizes thereof are not greaterthan 200 nanometers. In some embodiments preferably, the glass-ceramicsfurther comprise a second, different complex Al₂O₃.Y₂O₃. In someembodiments preferably, the glass-ceramics further comprise a complexAl₂O₃•REO.

Some embodiments of the present invention include glass-ceramicscomprising alpha Al₂O₃, crystalline ZrO₂, and a first complex Al₂O₃•REO,and wherein at least one of the alpha Al₂O₃, the crystalline ZrO₂, orthe first complex Al₂O₃•REO has an average crystal size not greater than150 nanometers. In some embodiments preferably, the glass-ceramicsfurther comprise a second, different complex Al₂O₃•REO. In someembodiments preferably, the glass-ceramics further comprise a complexAl₂O₃.Y₂O₃.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃•REO, a second, different complexAl₂O₃•REO, and crystalline ZrO₂, and wherein for at least one of thefirst complex Al₂O₃•REO, the second complex Al₂O₃•REO, or thecrystalline ZrO₂, at least 90 (in some embodiments preferably, 95, oreven 100) percent by number of the crystal sizes thereof are not greaterthan 200 nanometers. In some embodiments preferably, the glass-ceramicsfurther comprise a complex Al₂O₃.Y₂O₃.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃.Y₂O₃, a second, different complexAl₂O₃.Y₂O₃, and crystalline ZrO₂, and wherein at least one of the firstcomplex Al₂O₃.Y₂O₃, the second, different complex Al₂O₃.Y₂O₃, or thecrystalline ZrO₂ has an average crystal size not greater than 150nanometers. In some embodiments preferably, the glass-ceramics furthercomprise a second, different complex Al₂O₃.Y₂O₃. In some embodimentspreferably, the glass-ceramics further comprise a complex Al₂O₃•REO.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃.Y₂O₃, a second, different complexAl₂O₃.Y₂O₃, and crystalline ZrO₂, and wherein for at least one of thefirst complex Al₂O₃.Y₂O₃, the second, different complex Al₂O₃.Y₂O₃, orthe crystalline ZrO₂, at least 90 (in some embodiments preferably, 95,or even 100) percent by number of the crystal sizes thereof are notgreater than 200 nanometers. In some embodiments preferably, theglass-ceramics further comprise a complex Al₂O₃•REO.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃•REO, a second, different complexAl₂O₃•REO, and crystalline ZrO₂, and wherein at least one of the firstcomplex Al₂O₃•REO, the second, different complex Al₂O₃•REO, or thecrystalline ZrO₂ has an average crystal size not greater than 150nanometers. In some embodiments preferably, the glass-ceramics furthercomprise a second, different complex Al₂O₃•REO. In some embodimentspreferably, the glass-ceramics further comprise a complex Al₂O₃.Y₂O₃.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃•REO, a second, different complexAl₂O₃-REO, and crystalline ZrO₂, and wherein for at least one of thefirst complex Al₂O₃•REO, the second, different complex Al₂O₃•REO, or thecrystalline ZrO₂, at least 90 (in some embodiments preferably, 95, oreven 100) percent by number of the crystal sizes thereof are not greaterthan 200 nanometers. In some embodiments preferably, the glass-ceramicsfurther comprise a complex Al₂O₃.Y₂O₃.

In some embodiments, glass-ceramics according to the present inventioncomprise at least 75, 80, 85, 90, 95, 97, 98, 99, or even 100 percent byvolume crystallites, wherein the crystallites have an average size ofless than 1 micrometer. In some embodiments, glass-ceramics according tothe present invention comprise not greater than at least 75, 80, 85, 90,95, 97, 98, 99, or even 100 percent by volume crystallites, wherein thecrystallites have an average size not greater than 0.5 micrometer. Insome embodiments, glass-ceramics according to the present inventioncomprise less than at 75, 80, 85, 90, 95, 97, 98, 99, or even 100percent by volume crystallites, wherein the crystallites have an averagesize not greater than 0.3 micrometer. In some embodiments,glass-ceramics according to the present invention comprise less than atleast 75, 80, 85, 90, 95, 97, 98, 99, or even 100 percent by volumecrystallites, wherein the crystallites have an average size not greaterthan 0.15 micrometer.

Crystals formed by heat-treating amorphous to provide embodiments ofglass-ceramics according to the present invention may be, for example,equiaxed, columnar, or flattened splat-like features.

Although an amorphous material, glass-ceramic, etc. according to thepresent invention may be in the form of a bulk material, it is alsowithin the scope of the present invention to provide compositescomprising an amorphous material, glass-ceramic, etc. according to thepresent invention. Such a composite may comprise, for example, a phaseor fibers (continuous or discontinuous) or particles (includingwhiskers) (e.g., metal oxide particles, boride particles, carbideparticles, nitride particles, diamond particles, metallic particles,glass particles, and combinations thereof) dispersed in an amorphousmaterial, glass-ceramic, etc. according to the present invention,invention or a layered-composite structure (e.g., a gradient ofglass-ceramic to amorphous material used to make the glass-ceramicand/or layers of different compositions of glass-ceramics).

Typically, the (true) density, sometimes referred to as specificgravity, of ceramics according to the present invention is typically atleast 70% of theoretical density. More desirably, the (true) density ofceramic according to the present invention is at least 75%, 80%, 85%,90%, 92%, 95%, 96%, 97%, 98%, 99%, 99.5% or even 100% of theoreticaldensity. Abrasive particles according to the present invention havedensities of at least 85%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, 99.5% oreven 100% of theoretical density.

The average hardness of the material of the present invention can bedetermined as follows. Sections of the material are mounted in mountingresin (obtained under the trade designation “TRANSOPTIC POWDER” fromBuehler, Lake Bluff, Ill.) typically in a cylinder of resin about 2.5 cmin diameter and about 1.9 cm high. The mounted section is prepared usingconventional polishing techniques using a polisher (such as thatobtained from Buehler, Lake Bluff, Ill. under the trade designation“ECOMET 3”). The sample is polished for about 3 minutes with a diamondwheel, followed by 5 minutes of polishing with each of 45, 30, 15, 9, 3,and 1-micrometer slurries. The microhardness measurements are made usinga conventional microhardness tester (such as that obtained under thetrade designation “MITUTOYO MVK-VL” from Mitutoyo Corporation, Tokyo,Japan) fitted with a Vickers indenter using a 100-gram indent load. Themicrohardness measurements are made according to the guidelines statedin ASTM Test Method E384 Test Methods for Microhardness of Materials(1991), the disclosure of which is incorporated herein by reference.

In some embodiments, glass-ceramic according to the present inventionhave an average hardness of at least 13 GPa (in some embodimentspreferably, at least 14, 15, 16, 17, or even at least 18 GPa). Abrasiveparticles according to the present invention have an average hardness ofat least 15 GPa, in some embodiments, at least 16 GPa, at least 17 GPa,or even at least 18 GPa.

Additional details regarding amorphous materials and glass-ceramics,including making, using, and properties thereof, can be found inapplication having U.S. Ser. Nos. 09/922,526, 09/922,527, and09/922,530, filed Aug. 2, 2001, and U.S. Ser. Nos. 10/211,598;10/211,630; 10/211,639; 10/211,044; 10/211,628; 10/211,640; and10/211,684, filed the same date as the instant application, thedisclosures of which are incorporated herein by reference.

Abrasive particles according to the present invention generally comprisecrystalline ceramic (in some embodiments, preferably at least 75, 80,85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5, or even 100 percent byvolume) crystalline ceramic.

Abrasive particles according to the present invention can be screenedand graded using techniques well known in the art, including the use ofindustry recognized grading standards such as ANSI (American NationalStandard Institute), FEPA (Federation Europeenne des Fabricants deProducts Abrasifs), and JIS (Japanese Industrial Standard). Abrasiveparticles according to the present invention may be used in a wide rangeof particle sizes, typically ranging in size from about 0.1 to about5000 micrometers, more typically from about 1 to about 2000 micrometers;desirably from about 5 to about 1500 micrometers, more desirably fromabout 100 to about 1500 micrometers.

ANSI grade designations include: ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI24, ANSI 36, ANSI 40, ANSI 50, ANSI 60, ANSI 80, ANSI 100, ANSI 120,ANSI 150, ANSI 180, ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360,ANSI 400, and ANSI 600. Preferred ANSI grades comprising abrasiveparticles according to the present invention are ANSI 8–220. FEPA gradedesignations include P8, P12, P16, P24, P36, P40, P50, P60, P80, P100,P120, P150, P180, P220, P320, P400, P500, P600, P800, P1000, and P1200.Preferred FEPA grades comprising abrasive particles according to thepresent invention are P12–P220. JIS grade designations include JIS8,JIS12, JIS16, JIS24, JIS36, JIS46, JIS54, JIS60, JIS80, JIS100, JIS150,JIS180, JIS220, JIS240, JIS280, JIS320, JIS360, JIS400, JIS600, JIS800,JIS1000, JIS1500, JIS2500, JIS4000, JIS6000, JIS8000, and JIS10,000.Preferred JIS grades comprising abrasive particles according to thepresent invention are JIS8–220.

After crushing and screening, there will typically be a multitude ofdifferent abrasive particle size distributions or grades. Thesemultitudes of grades may not match a manufacturer's or supplier's needsat that particular time. To minimize inventory, it is possible torecycle the off demand grades back into melt to form amorphous material.This recycling may occur after the crushing step, where the particlesare in large chunks or smaller pieces (sometimes referred to as “fines”)that have not been screened to a particular distribution.

In another aspect, the present invention provides a method for makingabrasive particles, the method comprising heat-treating amorphous (e.g.,glass) comprising particles such that at least a portion of theamorphous material converts to a glass-ceramic to provide abrasiveparticles comprising the glass-ceramic. The present invention alsoprovides a method for making abrasive particles comprising aglass-ceramic, the method comprising heat-treating amorphous materialsuch that at least a portion of the amorphous material converts to aglass-ceramic, and crushing the resulting heat-treated material toprovide the abrasive particles. When crushed, glass tends to providesharper particles than crushing significantly crystallizedglass-ceramics or crystalline material.

In another aspect, the present invention provides agglomerate abrasivegrains each comprise a plurality of abrasive particles according to thepresent invention bonded together via a binder. In another aspect, thepresent invention provides an abrasive article (e.g., coated abrasivearticles, bonded abrasive articles (including vitrified, resinoid, andmetal bonded grinding wheels, cutoff wheels, mounted points, and honingstones), nonwoven abrasive articles, and abrasive brushes) comprising abinder and a plurality of abrasive particles, wherein at least a portionof the abrasive particles are abrasive particles (including where theabrasive particles are agglomerated) according to the present invention.Methods of making such abrasive articles and using abrasive articles arewell known to those skilled in the art. Furthermore, abrasive particlesaccording to the present invention can be used in abrasive applicationsthat utilize abrasive particles, such as slurries of abrading compounds(e.g., polishing compounds), milling media, shot blast media, vibratorymill media, and the like.

Coated abrasive articles generally include a backing, abrasiveparticles, and at least one binder to hold the abrasive particles ontothe backing. The backing can be any suitable material, including cloth,polymeric film, fibre, nonwoven webs, paper, combinations thereof, andtreated versions thereof. The binder can be any suitable binder,including an inorganic or organic binder (including thermally curableresins and radiation curable resins). The abrasive particles can bepresent in one layer or in two layers of the coated abrasive article.

An example of a coated abrasive article according to the presentinvention is depicted in FIG. 1. Referring to this figure, coatedabrasive article according to the present invention 1 has a backing(substrate) 2 and abrasive layer 3. Abrasive layer 3 includes abrasiveparticles according to the present invention 4 secured to a majorsurface of backing 2 by make coat 5 and size coat 6. In some instances,a supersize coat (not shown) is used.

Bonded abrasive articles typically include a shaped mass of abrasiveparticles held together by an organic, metallic, or vitrified binder.Such shaped mass can be, for example, in the form of a wheel, such as agrinding wheel or cutoff wheel. The diameter of grinding wheelstypically is about 1 cm to over 1 meter; the diameter of cut off wheelsabout 1 cm to over 80 cm (more typically 3 cm to about 50 cm). The cutoff wheel thickness is typically about 0.5 mm to about 5 cm, moretypically about 0.5 mm to about 2 cm. The shaped mass can also be in theform, for example, of a honing stone, segment, mounted point, disc (e.g.double disc grinder) or other conventional bonded abrasive shape. Bondedabrasive articles typically comprise about 3–50% by volume bondmaterial, about 30–90% by volume abrasive particles (or abrasiveparticle blends), up to 50% by volume additives (including grindingaids), and up to 70% by volume pores, based on the total volume of thebonded abrasive article.

A preferred form is a grinding wheel. Referring to FIG. 2, grindingwheel according to the present invention 10 is depicted, which includesabrasive particles according to the present invention 11, molded in awheel and mounted on hub 12.

Nonwoven abrasive articles typically include an open porous loftypolymer filament structure having abrasive particles according to thepresent invention distributed throughout the structure and adherentlybonded therein by an organic binder. Examples of filaments includepolyester fibers, polyamide fibers, and polyaramid fibers. In FIG. 3, aschematic depiction, enlarged about 100×, of a typical nonwoven abrasivearticle according to the present invention is provided. Such a nonwovenabrasive article according to the present invention comprises fibrousmat 50 as a substrate, onto which abrasive particles according to thepresent invention 52 are adhered by binder 54.

Useful abrasive brushes include those having a plurality of bristlesunitary with a backing (see, e.g., U.S. Pat. No. 5,427,595 (Pihl etal.), U.S. Pat. No. 5,443,906 (Pihl et al.), U.S. Pat. No. 5,679,067(Johnson et al.), and U.S. Pat. No. 5,903,951 (Ionta et al.), thedisclosure of which is incorporated herein by reference). Desirably,such brushes are made by injection molding a mixture of polymer andabrasive particles.

Suitable organic binders for making abrasive articles includethermosetting organic polymers. Examples of suitable thermosettingorganic polymers include phenolic resins, urea-formaldehyde resins,melamine-formaldehyde resins, urethane resins, acrylate resins,polyester resins, aminoplast resins having pendant α,β-unsaturatedcarbonyl groups, epoxy resins, acrylated urethane, acrylated epoxies,and combinations thereof. The binder and/or abrasive article may alsoinclude additives such as fibers, lubricants, wetting agents,thixotropic materials, surfactants, pigments, dyes, antistatic agents(e.g., carbon black, vanadium oxide, graphite, etc.), coupling agents(e.g., silanes, titanates, zircoaluminates, etc.), plasticizers,suspending agents, and the like. The amounts of these optional additivesare selected to provide the desired properties. The coupling agents canimprove adhesion to the abrasive particles and/or filler. The binderchemistry may thermally cured, radiation cured or combinations thereof.Additional details on binder chemistry may be found in U.S. Pat. No.4,588,419 (Caul et al.), U.S. Pat. No. 4,751,138 (Tumey et al.), andU.S. Pat. No. 5,436,063 (Follett et al.), the disclosures of which areincorporated herein by reference.

More specifically with regard to vitrified bonded abrasives, vitreousbonding materials, which exhibit an amorphous structure and aretypically hard, are well known in the art. In some cases, the vitreousbonding material includes crystalline phases. Bonded, vitrified abrasivearticles according to the present invention may be in the shape of awheel (including cut off wheels), honing stone, mounted pointed or otherconventional bonded abrasive shape. A preferred vitrified bondedabrasive article according to the present invention is a grinding wheel.

Examples of metal oxides that are used to form vitreous bondingmaterials include: silica, silicates, alumina, soda, calcia, potassia,titania, iron oxide, zinc oxide, lithium oxide, magnesia, boria,aluminum silicate, borosilicate glass, lithium aluminum silicate,combinations thereof, and the like. Typically, vitreous bondingmaterials can be formed from composition comprising from 10 to 100%glass frit, although more typically the composition comprises 20% to 80%glass frit, or 30% to 70% glass frit. The remaining portion of thevitreous bonding material can be a non-frit material. Alternatively, thevitreous bond may be derived from a non-frit containing composition.Vitreous bonding materials are typically matured at a temperature(s) ina range of about 700° C. to about 1500° C., usually in a range of about800° C. to about 1300° C., sometimes in a range of about 900° C. toabout 1200° C., or even in a range of about 950° C. to about 1100° C.The actual temperature at which the bond is matured depends, forexample, on the particular bond chemistry.

Preferred vitrified bonding materials may include those comprisingsilica, alumina (desirably, at least 10 percent by weight alumina), andboria (desirably, at least 10 percent by weight boria). In most casesthe vitrified bonding material further comprise alkali metal oxide(s)(e.g., Na₂O and K₂O) (in some cases at least 10 percent by weight alkalimetal oxide(s)).

Binder materials may also contain filler materials or grinding aids,typically in the form of a particulate material. Typically, theparticulate materials are inorganic materials. Examples of usefulfillers for this invention include: metal carbonates (e.g., calciumcarbonate (e.g., chalk, calcite, marl, travertine, marble andlimestone), calcium magnesium carbonate, sodium carbonate, magnesiumcarbonate), silica (e.g., quartz, glass beads, glass bubbles and glassfibers) silicates (e.g., talc, clays, (montmorillonite) feldspar, mica,calcium silicate, calcium metasilicate, sodium aluminosilicate, sodiumsilicate) metal sulfates (e.g., calcium sulfate, barium sulfate, sodiumsulfate, aluminum sodium sulfate, aluminum sulfate), gypsum,vermiculite, wood flour, aluminum trihydrate, carbon black, metal oxides(e.g., calcium oxide (lime), aluminum oxide, titanium dioxide), andmetal sulfites (e.g., calcium sulfite).

In general, the addition of a grinding aid increases the useful life ofthe abrasive article. A grinding aid is a material that has asignificant effect on the chemical and physical processes of abrading,which results in improved performance. Although not wanting to be boundby theory, it is believed that a grinding aid(s) will (a) decrease thefriction between the abrasive particles and the workpiece being abraded,(b) prevent the abrasive particles from “capping” (i.e., prevent metalparticles from becoming welded to the tops of the abrasive particles),or at least reduce the tendency of abrasive particles to cap, (c)decrease the interface temperature between the abrasive particles andthe workpiece, or (d) decreases the grinding forces.

Grinding aids encompass a wide variety of different materials and can beinorganic or organic based. Examples of chemical groups of grinding aidsinclude waxes, organic halide compounds, halide salts and metals andtheir alloys. The organic halide compounds will typically break downduring abrading and release a halogen acid or a gaseous halide compound.Examples of such materials include chlorinated waxes liketetrachloronaphthalene, pentachloronaphthalene, and polyvinyl chloride.Examples of halide salts include sodium chloride, potassium cryolite,sodium cryolite, ammonium cryolite, potassium tetrafluoroborate, sodiumtetrafluoroborate, silicon fluorides, potassium chloride, and magnesiumchloride. Examples of metals include, tin, lead, bismuth, cobalt,antimony, cadmium, and iron titanium. Other miscellaneous grinding aidsinclude sulfur, organic sulfur compounds, graphite, and metallicsulfides. It is also within the scope of the present invention to use acombination of different grinding aids, and in some instances this mayproduce a synergistic effect. The preferred grinding aid is cryolite;the most preferred grinding aid is potassium tetrafluoroborate.

Grinding aids can be particularly useful in coated abrasive and bondedabrasive articles. In coated abrasive articles, grinding aid istypically used in the supersize coat, which is applied over the surfaceof the abrasive particles. Sometimes, however, the grinding aid is addedto the size coat. Typically, the amount of grinding aid incorporatedinto coated abrasive articles are about 50–300 g/m² (desirably, about80–160 g/m²). In vitrified bonded abrasive articles grinding aid istypically impregnated into the pores of the article.

The abrasive articles can contain 100% abrasive particles according tothe present invention, or blends of such abrasive particles with otherabrasive particles and/or diluent particles. However, at least about 2%by weight, desirably at least about 5% by weight, and more desirablyabout 30–100% by weight, of the abrasive particles in the abrasivearticles should be abrasive particles according to the presentinvention. In some instances, the abrasive particles according thepresent invention may be blended with another abrasive particles and/ordiluent particles at a ratio between 5 to 75% by weight, about 25 to 75%by weight about 40 to 60% by weight, or about 50% to 50% by weight(i.e., in equal amounts by weight). Examples of suitable conventionalabrasive particles include fused aluminum oxide (including white fusedalumina, heat-treated aluminum oxide and brown aluminum oxide), siliconcarbide, boron carbide, titanium carbide, diamond, cubic boron nitride,garnet, fused alumina-zirconia, and sol-gel-derived abrasive particles,and the like. The sol-gel-derived abrasive particles may be seeded ornon-seeded. Likewise, the sol-gel-derived abrasive particles may berandomly shaped or have a shape associated with them, such as a rod or atriangle. Examples of sol-gel abrasive particles include those describedU.S. Pat. No. 4,314,827 (Leitheiser et al.), U.S. Pat. No. 4,518,397(Leitheiser et al.), U.S. Pat. No. 4,623,364 (Cottringer et al.), U.S.Pat. No. 4,744,802 (Schwabel), U.S. Pat. No. 4,770,671 (Monroe et al.),U.S. Pat. No. 4,881,951 (Wood et al.), U.S. Pat. No. 5,011,508 (Wald etal.), U.S. Pat. No. 5,090,968 (Pellow), U.S. Pat. No. 5,139,978 (Wood),U.S. Pat. No. 5,201,916 (Berg et al.), U.S. Pat. No. 5,227,104 (Bauer),U.S. Pat. No. 5,366,523 (Rowenhorst et al.), U.S. Pat. No. 5,429,647(Larmie), U.S. Pat. No. 5,498,269 (Larmie), and U.S. Pat. No. 5,551,963(Larmie), the disclosures of which are incorporated herein by reference.Additional details concerning sintered alumina abrasive particles madeby using alumina powders as a raw material source can also be found, forexample, in U.S. Pat. No. 5,259,147 (Falz), U.S. Pat. No. 5,593,467(Monroe), and U.S. Pat. No. 5,665,127 (Moltgen), the disclosures ofwhich are incorporated herein by reference. Additional detailsconcerning fused abrasive particles, can be found, for example, in U.S.Pat. No. 1,161,620 (Coulter), U.S. Pat. No. 1,192,709 (Tone), U.S. Pat.No. 1,247,337 (Saunders et al.), U.S. Pat. No. 1,268,533 (Allen), andU.S. Pat. No. 2,424,645 (Baumann et al.), U.S. Pat. No. 3,891,408 (Rowseet al.), U.S. Pat. No. 3,781,172 (Pett et al.), U.S. Pat. No. 3,893,826(Quinan et al.), U.S. Pat. No. 4,126,429 (Watson), U.S. Pat. No.4,457,767 (Poon et al.), U.S. Pat. No. 5,023,212 (Dubots et al.), U.S.Pat. No. 5,143,522 (Gibson et al.), and U.S. Pat. No. 5,336,280 (Dubotset al.), and applications having U.S. Ser. Nos. 09/495,978, 09/496,422,09/496,638, and 09/496,713, each filed on Feb. 2, 2000, and, U.S. Ser.Nos. 09/618,876, 09/618,879, 09/619,106, 09/619,191, 09/619,192,09/619,215, 09/619,289, 09/619,563, 09/619,729, 09/619,744, and09/620,262, each filed on Jul. 19, 2000, and U.S. Ser. No. 09/772,730,filed Jan. 30, 2001, the disclosures of which are incorporated herein byreference. In some instances, blends of abrasive particles may result inan abrasive article that exhibits improved grinding performance incomparison with abrasive articles comprising 100% of either type ofabrasive particle.

If there is a blend of abrasive particles, the abrasive particle typesforming the blend may be of the same size. Alternatively, the abrasiveparticle types may be of different particle sizes. For example, thelarger sized abrasive particles may be abrasive particles according tothe present invention, with the smaller sized particles being anotherabrasive particle type. Conversely, for example, the smaller sizedabrasive particles may be abrasive particles according to the presentinvention, with the larger sized particles being another abrasiveparticle type.

Examples of suitable diluent particles include marble, gypsum, flint,silica, iron oxide, aluminum silicate, glass (including glass bubblesand glass beads), alumina bubbles, alumina beads and diluentagglomerates. Abrasive particles according to the present invention canalso be combined in or with abrasive agglomerates. Abrasive agglomerateparticles typically comprise a plurality of abrasive particles, abinder, and optional additives. The binder may be organic and/orinorganic. Abrasive agglomerates may be randomly shape or have apredetermined shape associated with them. The shape may be a block,cylinder, pyramid, coin, square, or the like. Abrasive agglomerateparticles typically have particle sizes ranging from about 100 to about5000 micrometers, typically about 250 to about 2500 micrometers.Additional details regarding abrasive agglomerate particles may befound, for example, in U.S. Pat. No. 4,311,489 (Kressner), U.S. Pat. No.4,652,275 (Bloecher et al.), U.S. Pat. No. 4,799,939 (Bloecher et al.),U.S. Pat. No. 5,549,962 (Holmes et al.), and U.S. Pat. No. 5,975,988(Christianson), and applications having U.S. Ser. Nos. 09/688,444 and09/688,484, filed Oct. 16, 2000, the disclosures of which areincorporated herein by reference.

The abrasive particles may be uniformly distributed in the abrasivearticle or concentrated in selected areas or portions of the abrasivearticle. For example, in a coated abrasive, there may be two layers ofabrasive particles. The first layer comprises abrasive particles otherthan abrasive particles according to the present invention, and thesecond (outermost) layer comprises abrasive particles according to thepresent invention. Likewise in a bonded abrasive, there may be twodistinct sections of the grinding wheel. The outermost section maycomprise abrasive particles according to the present invention, whereasthe innermost section does not. Alternatively, abrasive particlesaccording to the present invention may be uniformly distributedthroughout the bonded abrasive article.

Further details regarding coated abrasive articles can be found, forexample, in U.S. Pat. No. 4,734,104 (Broberg), U.S. Pat. No. 4,737,163(Larkey), U.S. Pat. No. 5,203,884 (Buchanan et al.), U.S. Pat. No.5,152,917 (Pieper et al.), U.S. Pat. No. 5,378,251 (Culler et al.), U.S.Pat. No. 5,417,726 (Stout et al.), U.S. Pat. No. 5,436,063 (Follett etal.), U.S. Pat. No. 5,496,386 (Broberg et al.), U.S. Pat. No. 5,609,706(Benedict et al.), U.S. Pat. No. 5,520,711 (Helmin), U.S. Pat. No.5,954,844 (Law et al.), U.S. Pat. No. 5,961,674 (Gagliardi et al.), andU.S. Pat. No. 5,975,988 (Christianson), the disclosures of which areincorporated herein by reference. Further details regarding bondedabrasive articles can be found, for example, in U.S. Pat. No. 4,543,107(Rue), U.S. Pat. No. 4,741,743 (Narayanan et al.), U.S. Pat. No.4,800,685 (Haynes et al.), U.S. Pat. No. 4,898,597 (Hay et al.), U.S.Pat. No. 4,997,461 (Markhoff-Matheny et al.), U.S. Pat. No. 5,037,453(Narayanan et al.), U.S. Pat. No. 5,110,332 (Narayanan et al.), and U.S.Pat. No. 5,863,308 (Qi et al.) the disclosures of which are incorporatedherein by reference. Further details regarding vitreous bonded abrasivescan be found, for example, in U.S. Pat. No. 4,543,107 (Rue), U.S. Pat.No. 4,898,597 (Hay et al.), U.S. Pat. No. 4,997,461 (Markhoff-Matheny etal.), U.S. Pat. No. 5,094,672 (Giles Jr. et al.), U.S. Pat. No.5,118,326 (Sheldon et al.), U.S. Pat. No. 5,131,926 (Sheldon et al.),U.S. Pat. No. 5,203,886 (Sheldon et al.), U.S. Pat. No. 5,282,875 (Woodet al.), U.S. Pat. No. 5,738,696 (Wu et al.), and U.S. Pat. No.5,863,308 (Qi), the disclosures of which are incorporated herein byreference. Further details regarding nonwoven abrasive articles can befound, for example, in U.S. Pat. No. 2,958,593 (Hoover et al.), thedisclosure of which is incorporated herein by reference.

The present invention provides a method of abrading a surface, themethod comprising contacting at least one abrasive particle according tothe present invention, with a surface of a workpiece; and moving atleast of one the abrasive particle or the contacted surface to abrade atleast a portion of said surface with the abrasive particle. Methods forabrading with abrasive particles according to the present inventionrange of snagging (i.e., high pressure high stock removal) to polishing(e.g., polishing medical implants with coated abrasive belts), whereinthe latter is typically done with finer grades (e.g., less ANSI 220 andfiner) of abrasive particles. The abrasive particle may also be used inprecision abrading applications, such as grinding cam shafts withvitrified bonded wheels. The size of the abrasive particles used for aparticular abrading application will be apparent to those skilled in theart.

Abrading with abrasive particles according to the present invention maybe done dry or wet. For wet abrading, the liquid may be introducedsupplied in the form of a light mist to complete flood. Examples ofcommonly used liquids include: water, water-soluble oil, organiclubricant, and emulsions. The liquid may serve to reduce the heatassociated with abrading and/or act as a lubricant. The liquid maycontain minor amounts of additives such as bactericide, antifoamingagents, and the like.

Abrasive particles according to the present invention may be used toabrade workpieces such as aluminum metal, carbon steels, mild steels,tool steels, stainless steel, hardened steel, titanium, glass, ceramics,wood, wood like materials, paint, painted surfaces, organic coatedsurfaces and the like. The applied force during abrading typicallyranges from about 1 to about 100 kilograms.

Other examples of uses of embodiments of amorphous materials and/orglass-ceramics according to the present invention include as solidelectrolytes in such applications as solid state batteries, solid oxidefuel cells and other electrochemical devices; as hosts for radioactivewastes and surplus actinides; as oxidation catalysts; as oxygenmonitoring sensors; as hosts for fluorescence centers; durable IRtransmitting window materials; and armor. For example, pyrochlore typeof rare earth zirconium oxides (Re₂Zr₂O₇) are known to be useful phasesfor the above-mentioned radioactive wastes, surplus actinides, oxidationcatalysts, oxygen monitoring sensors, and fluorescence centersapplications. Further, for example, Ce-containing mixed oxides are knownas oxidation catalysts. Although not wanting to be bound by theory, itis believed that the redox properties and the relatively high oxygenstorage capacity of the Ce-containing mixed oxides aid in oxidationcatalysts. With regard to durable IR transmitting window materialsapplications uses include those involving moisture, impact by solid andliquid particles, high temperatures, and rapid heating rates.

Advantages and embodiments of this invention are further illustrated bythe following examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention. All parts andpercentages are by weight unless otherwise indicated. Unless otherwisestated, all examples contained no significant amount of SiO₂, B₂O₃,P₂O₅, GeO₂, TeO₂, As₂O₃, and V₂O₅.

EXAMPLES Examples 1–20

A 250-ml polyethylene bottle (7.3-cm diameter) was charged with a50-gram mixture of various powders (as shown below in Table 1, withsources of the raw materials listed in Table 2), 75 grams of isopropylalcohol, and 200 grams of alumina milling media (cylindrical shape, bothheight and diameter of 0.635 cm; 99.9% alumina; obtained from Coors,Golden, Colo.). The contents of the polyethylene bottle were milled for16 hours at 60 revolutions per minute (rpm). After the milling, themilling media were removed and the slurry was poured onto a warm(approximately 75° C.) glass (“PYREX”) pan and dried. The dried mixturewas screened through a 70-mesh screen (212-micrometer opening size) withthe aid of a paint brush.

After grinding and screening, the mixture of milled feed particles wasfed slowly (0.5 gram/minute) into a hydrogen/oxygen torch flame to meltthe particles. The torch used to melt the particles, thereby generatingmolten droplets, was a Bethlehem bench burner PM2D Model B obtained fromBethlehem Apparatus Co., Hellertown, Pa. Hydrogen and oxygen flow ratesfor the torch were as follows. For the inner ring, the hydrogen flowrate was 8 standard liters per minute (SLPM) and the oxygen flow ratewas 3.5 SLPM. For the outer ring, the hydrogen flow rate was 23 SLPM andthe oxygen flow rate was 12 SLPM. The dried and sized particles were fedslowly (0.5 gram/minute) into the torch flame which melted the particlesand carried them into a 19-liter (5-gallon) cylindrical container (30 cmdiameter by 34 cm height) of continuously circulating, turbulent waterto rapidly quench the molten droplets. The angle at which the flame hitthe water was approximately 45°, and the flame length, burner to watersurface, was approximately 18 centimeters (cm). The resulting molten andrapidly quenched particles were collected and dried at 110° C. Theparticles were spherical in shape and varied in size from a fewmicrometers (i.e., microns) up to 250 micrometers.

A percent amorphous yield was calculated from the resulting flame-formedbeads using a −100+120 mesh size fraction (i.e., the fraction collectedbetween 150-micrometer opening size and 125-micrometeropening sizescreens). The measurements were done in the following manner. A singlelayer of beads was spread out upon a glass slide. The beads wereobserved using an optical microscope. Using the crosshairs in theoptical microscope eyepiece as a guide, beads that lay along a straightline were counted either amorphous or crystalline depending on theiroptical clarity. A total of 500 beads were counted and a percentamorphous yield was determined by the amount of amorphous beads dividedby total beads counted.

Materials prepared in Examples 12 through 20 were amorphous asdetermined by visual inspection, but the quantitative analysis accordingto the above procedure was not performed. Amorphous material istypically transparent due to the lack of light scattering centers suchas crystal boundaries, while the crystalline particles show acrystalline structure and are opaque due to light scattering effects.

The phase composition (glassy/amorphous/crystalline) was determinedthrough Differential Thermal Analysis (DTA) as described below. Thematerial was classified as amorphous if the corresponding DTA trace ofthe material contained an exothermic crystallization event (T_(x)). Ifthe same trace also contained an endothermic event (T_(g)) at atemperature lower than T_(x) it was considered to consist of a glassphase. If the DTA trace of the material contained no such events, it wasconsidered to contain crystalline phases.

Differential thermal analysis (DTA) was conducted using the followingmethod. DTA runs were made (using an instrument obtained from NetzschInstruments, Selb, Germany under the trade designation “NETZSCH STA 409DTA/TGA”) using a −140+170 mesh size fraction (i.e., the fractioncollected between 105-micrometer opening size and 90-micrometer openingsize screens). The amount of each screened sample placed in a100-microliter AL₂O₃ sample holder was about 400 milligrams. Each samplewas heated in static air at a rate of 10° C./minute from roomtemperature (about 25° C.) to 1100° C.

Referring to FIG. 4, line 123 is the plotted DTA data for the Example 1material. Referring to FIG. 4, line 123, the material exhibited anendothermic event at temperature around 872° C., as evidenced by thedownward curve of line 123. It is believed this event was due to theglass transition (T_(g)) of the glass material. At about 958° C., anexothermic event was observed as evidenced by the sharp peak in line123. It is believed that this event was due to the crystallization(T_(x)) of the material. These T_(g) and T_(x) values for otherexamples, except for Examples 15–20, are reported in Table 1 below.

TABLE 1 Percent final Percent Glass transition/ Batch Weight percentFinal weight alumina from amorphous crystallization Example amounts, gof components percent alumina % Al metal yield temperatures Ex. 1 Al₂O₃:19.3 Al₂O₃: 38.5 ALZ La₂O₃: 21.3 La₂O₃: 42.5 882° C. ZrO₂: 9.5 ZrO₂:19.0 38.5 0 98 932° C. Ex. 2 Al₂O₃: 16.7 Al₂O₃: 33.3 AYZ Al: 8.8 Al:17.6 Y₂O₃: 16 Y₂O₃: 31.9 900° C. ZrO₂: 8.6 ZrO₂: 17.2 57.5 50 89 935° C.Ex. 3 Al₂O₃: 20.5 Al₂O₃: 41.0 872° C. AGdZ Gd₂O₃: 20.5 Gd₂O₃: 41.0 ZrO₂:9 ZrO₂: 18 41.0 0 94 Ex. 4 Al₂O₃: 19.5 Al₂O₃: 39.1 AY Al: 10.3 Al: 20.7894° C. Y₂O₃: 20.1 Y₂O₃: 40.3 66 50 93 943° C. Ex. 5 Al₂O₃: 18.8 Al₂O₃:37.7 AYMg Al: 10.0 Al: 19.9 MgO: 0.0 MgO: 0.0 Mg: 1.8 Mg: 3.6 848° C.Y₂O₃: 19.4 Y₂O₃: 38.8 62.7 50 93 996° C. Ex. 6 Al₂O₃: 18.1 Al₂O₃: 36.2AYMg Al: 9.6 Al: 19.2 MgO: 0.0 MgO: 0.0 Mg: 3.7 Mg: 7.3 832° C. Y₂O₃:18.6 Y₂O₃: 37.3 59.4 50 81 884° C. Ex. 7 Al₂O₃: 17.0 Al₂O₃: 33.9 none AZAl: 9.0 Al: 18.0 58.5 50 63 959° C. ZrO₂: 24.1 ZrO₂: 48.1 Ex. 8 Al₂O₃:15.5 Al₂O₃: 31.0 AZ-Ti Al: 8.2 Al: 16.4 ZrO₂: 22.0 ZrO₂: 44.0 none TiO₂:4.3 TiO₂: 8.6 54 50 79 936° C. Ex. 9 Al₂O₃: 12.3 Al₂O₃: 24.5 AZ-La Al:6.5 Al: 13.0 ZrO₂: 17.4 ZrO₂: 34.8 889° C. La₂O₃: 13.8 La₂O₃: 27.7 44 5094 918° C. Ex. 10 Al₂O₃: 9.1 Al₂O₃: 18.2 AZ-La Al: 4.8 Al: 9.6 ZrO₂:13.0 ZrO₂: 25.9 868° C. La₂O₃: 23.1 La₂O₃: 46.2 34 50 96 907° C. Ex. 11Al₂O₃: 7.5 Al₂O₃: 15.0 AZ-La Al: 4.0 Al: 8.0 ZrO₂: 17.0 ZrO₂: 34.0 870°C. La₂O₃: 21.4 La₂O₃: 42.8 28 50 93 898° C. Ex. 12 Al₂O₃: 20.3 Al₂O₃:40.6 ACZ ZrO₂: 9.0 ZrO₂: 18.0 838° C. La₂O₃: 20.7 La₂O₃: 41.4 40.6 0 NA908° C. Ex. 13 Al₂O₃: 15.6 Al₂O₃: 31.2 ALZ/ La₂O₃: 17 La₂O₃: 34 CaF₂ZrO₂: 7.4 ZrO₂: 14.8 CaF₂: 10 CaF2: 20 none 37.04 0 NA 676° C. Ex. 14Al₂O₃: 17.87 Al₂O₃: 35.73 ALZ/ La₂O₃: 21.08 La₂O₃: 42.17 P₂O₅ ZrO₂: 8.55ZrO₂: 17.1 P₂O₅: 2.5 P₂O₅: 5 857° C. 35.73 0 NA 932° C. Ex. 15 Al₂O₃:17.87 Al₂O₃: 35.73 ALZ/ La₂O₃: 21.08 La₂O₃: 42.17 Nb₂O₅ ZrO₂: 8.55 ZrO₂:17.1 Nb₂O₅: 2.5 Nb₂O₅: 5 35.73 0 NA NA Ex. 16 Al₂O₃: 17.87 Al₂O₃: 35.73ALZ/ La₂O₃: 21.08 La₂O₃: 42.17 Ta₂O₅ ZrO₂: 8.55 ZrO₂: 17.1 Ta₂O₅: 2.5Ta₂O₅: 5 NA 35.73 0 NA Ex. 17 Al₂O₃: 17.87 Al₂O₃: 35.73 ALZ/ La₂O₃:21.08 La₂O₃: 42.17 SrO ZrO₂: 8.55 ZrO₂: 17.1 SrO: 2.5 SrO: 5 NA 35.73 0NA Ex. 18 Al₂O₃: 17.87 Al₂O₃: 35.73 ALZ/ La₂O₃: 21.08 La₂O₃: 42.17 Mn₂O₃ZrO₂: 8.55 ZrO₂: 17.1 Mn₂O₃: 2.5 Mn₂O₃: 5 NA 35.73 0 NA Ex. 19 Al₂O₃:18.25 Al₂O₃: 36.5 ALZ/ La₂O₃: 21.52 La₂O₃: 43.04 Fe₂O₃ ZrO₂: 8.73 ZrO₂:17.46 Fe₂O₃: 1.5 Fe₂O₃: 3 NA 36.5 0 NA Ex. 20 Al₂O₃: 18.25 Al₂O₃: 36.5ALZ/ La₂O₃: 21.52 La₂O₃: 43.04 Cr₂O₃ ZrO₂: 8.73 ZrO₂: 17.46 Cr₂O₃: 1.5Cr₂O₃: 3 NA 36.5 0 NA NA means not measured.

TABLE 2 Raw Material Source Alumina particles (Al₂O₃) Obtained fromAlcoa Industrial Chemicals, Bauxite, AR, under the trade designation“A16SG” Aluminum particles (Al) Obtained from Alfa Aesar, Ward Hill, MACerium oxide particles Obtained from Rhone-Poulence, France Gadoliniumoxide particles Obtained from Molycorp Inc., Mountain Pass, CA Lanthanumoxide particles (La₂O₃) Obtained from Molycorp Inc., Mountain Pass, CAand calcined at 700° C. for 6 hours prior to batch mixing. Magnesiumparticles (Mg) Obtained from Alfa Aesar, Ward Hill, MA Magnesium oxideparticles (MgO) Obtained from BDH Chemicals Ltd, Poole, England Titaniumoxide particles (TiO₂) Obtained from Kemira, Savannah, GA, under thetrade designation “Unitane 0–110” Yttrium oxide particles (Y₂O₃)Obtained from H.C. Stark Newton, MA Zirconium oxide particles (ZrO₂)Obtained from Zirconia Sales, Inc. of Marietta, GA under the tradedesignation “DK-2” Calcium fluoride particles (CaF₂) Obtained fromAldrich, Milwaukee, WI Phosphorous oxide particles (P₂O₅) Obtained fromAldrich, Milwaukee, WI Niobium oxide particles (Nb₂O₅) Obtained fromAldrich, Milwaukee, WI Tantalum oxide particles (Ta₂O₅) Obtained fromAldrich, Milwaukee, WI Strontium oxide particles (SrO) Obtained fromAldrich, Milwaukee, WI Manganese oxide particles (Mn₂O₃) Obtained fromAldrich, Milwaukee, WI Iron oxide particles (Fe₂O₃) Obtained fromAldrich, Milwaukee, WI Chromium oxide particles (Cr₂O₃) Obtained fromAldrich, Milwaukee, WI

Example 21

About 25 grams of the beads from Example 1 were placed in a graphite dieand hot-pressed using uniaxial pressing apparatus (obtained under thetrade designation “HP-50”, Thermal Technology Inc., Brea, Calif.). Thehot-pressing was carried out in an argon atmosphere and 13.8 megapascals(MPa) (2000 pounds per square inch or 2 ksi) pressure. The hot-pressingfurnace was ramped up to 970° C., at 25° C./minute. The result was adisc, 3.4 cm in diameter and 0.6 cm thick, of transparent bulk material.A DTA trace was conducted as described in Example 1–20. The traceexhibited an endothermic event at temperature around 885° C., asevidenced by the downward change in the curve of the trace. It isbelieved this event was due to the glass transition (T_(g)) of the glassmaterial. The same material exhibited an exothermic event at atemperature around 928° C., as evidenced by the sharp peak in the trace.It is believed that this event was due to the crystallization (T_(x)) ofthe material.

Example 22

A 250-ml polyethylene bottle (7.3-cm diameter) was charged with thefollowing 50-gram mixture: 19.3 grams of alumina particles (obtainedfrom Alcoa Industrial Chemicals, Bauxite, Ark., under the tradedesignation “Al6SG”), 9.5 grams of zirconium oxide particles (obtainedfrom Zirconia Sales, Inc. of Marietta, Ga. under the trade designation“DK-2”), and 21.2 grams of lanthanum oxide particles (obtained fromMolycorp Inc., Mountain Pass, Calif.), 75 grams of isopropyl alcohol,and 200 grams of alumina milling media (cylindrical in shape, bothheight and diameter of 0.635 cm; 99.9% alumina; obtained from Coors,Golden, Colo.). The contents of the polyethylene bottle were milled for16 hours at 60 revolutions per minute (rpm). The ratio of alumina tozirconia in the starting material was 2:1, and the alumina and zirconiacollectively made up about 58 weight percent (wt-%). After the milling,the milling media were removed and the slurry was poured onto a warm(approximately 75° C.) glass (“PYREX”) pan and dried. The dried mixturewas screened through a 70-mesh screen (212-micrometer opening size) withthe aid of a paint brush.

After grinding and screening, the mixture of milled feed particles wasfed slowly (0.5 gram/minute) into a hydrogen/oxygen torch flame to meltthe particles. The torch used to melt the particles, thereby generatingmolten droplets, was a Bethlehem bench burner PM2D Model B obtained fromBethlehem Apparatus Co., Hellertown, Pa. Hydrogen and oxygen flow ratesfor the torch were as follows. For the inner ring, the hydrogen flowrate was 8 standard liters per minute (SLPM) and the oxygen flow ratewas 3.5 SLPM. For the outer ring, the hydrogen flow rate was 23 SLPM andthe oxygen flow rate was 12 SLPM. The dried and sized particles were fedslowly (0.5 gram/minute) into the torch flame, which melted theparticles and carried them on to an inclined stainless steel surface(approximately 51 centimeters (20 inches) wide with a slope angle of 45degrees) with cold water running over (approximately 8 liters/minute)the surface to rapidly quench the molten droplets. The resulting moltenand quenched beads were collected and dried at 110° C. The particleswere spherical in shape and varied in size from a few micrometers (i.e.,microns) up to 250 micrometers.

Subsequently, the flame-formed beads having diameters less than 125micrometers were then passed through a plasma gun and deposited onstainless steel substrates as follows.

Four 304 stainless steel substrates (76.2 millimeter (mm)×25.4 mm×3.175mm dimensions), and two 1080 carbon steel substrates (76.2 mm×25.4mm×1.15 mm) were prepared in the following manner. The sides to becoated were sandblasted, washed in an ultrasonic bath, and then wipedclean with isopropyl alcohol. Four stainless steel and one 1080 carbonsteel substrates were placed approximately 10 centimeters (cm) in frontof the nozzle of a plasma gun (obtained under the trade designation“Praxair SG-100 Plasma Gun” from Praxair Surface Technologies, Concord,N.H.). The second 1080 carbon steel was placed 18 cm in front of thenozzle of the plasma gun. The coatings made on the second 1080 carbonsteel samples at a distance of 18 cm in front of the nozzle of theplasma gun were not further characterized.

The plasma unit had a power rating of 40 kW. The plasma gas was argon(50 pounds per square inch (psi), 0.3 megapascal (MPa)) with helium asthe auxiliary gas (150 psi, 1 MPa). The beads were passed through theplasma gun by using argon as the carrier gas (50 psi, 0.3 MPa) using aPraxair Model 1270 computerized powder feeder (obtained from PraxairSurface Technologies, Concord, N.H.). During deposition, a potential ofabout 40 volts and a current of about 900 amperes was applied and theplasma gun was panned left to right, up and down, to evenly coat thesubstrates. When the desired thickness was achieved, the plasma spraywas shut off and the samples were recovered. The 1080 carbon steelsubstrate was flexed, thus separating the coating from the substrateresulting in a free-standing bulk material. The deposited material had az dimension (thickness) of about 1350 micrometers, as determined usingoptical microscopy.

The phase composition (glassy/amorphous/crystalline) was determinedthrough Differential Thermal Analysis (DTA) as described below. Thematerial was classified as amorphous if the corresponding DTA trace ofthe material contained an exothermic crystallization event (T_(x)). Ifthe same trace also contained an endothermic event (T_(g)) at atemperature lower than T_(x) it was considered to consist of a glassphase. If the DTA trace of the material contained no such events, it wasconsidered to contain crystalline phases.

Differential thermal analysis (DTA) was conducted using the followingmethod. DTA runs were made (using an instrument obtained from NetzschInstruments, Selb, Germany under the trade designation “NETZSCH STA 409DTA/TGA”) using a −140+170 mesh size fraction (i.e., the fractioncollected between 105-micrometer opening size and 90-micrometer openingsize screens). The amount of each screened sample placed in a100-microliter Al₂O₃ sample holder was about 400 milligrams. Each samplewas heated in static air at a rate of 10° C./minute from roomtemperature (about 25° C.) to 1100° C.

The coated material (on 304 stainless steel substrates) exhibited anendothermic event at a temperature around 880° C., as evidenced by adownward change in the curve of the trace. It is believed this event wasdue to the glass transition (T_(g)) of the glass material. The samematerial exhibited an exothermic event at a temperature around 931° C.,as evidenced by a sharp peak in the trace. It is believed that thisevent was due to the crystallization (T_(x)) of the material. Thus, thecoated material (on 304 stainless steel substrates) and thefree-standing bulk material were glassy as determined by a DTA trace.

A portion of the glassy free-standing bulk material was thenheat-treated at 1300° C. for 48 hours. Powder X-ray diffraction, XRD,(using an X-ray diffractometer (obtained under the trade designation“PHILLIPS XRG 3100” from Phillips, Mahwah, N.J.) with copper K α1radiation of 1.54050 Angstrom)) was used to determine the phasespresent. The phases were determined by comparing the peaks present inthe XRD trace of the crystallized material to XRD patterns ofcrystalline phases provided in JCPDS (Joint Committee on PowderDiffraction Standards) databases, published by International Center forDiffraction Data. The resulting crystalline material included LaAlO₃,ZrO₂ (cubic, tetragonal), LaAl₁₁O₁₈, and transitional Al₂O₃ phases.

Another portion of the glassy free-standing bulk material wascrystallized at 1300° C. for 1 hour in an electrically heated furnace(obtained from CM Furnaces, Bloomfield, N.J. under the trade designation“Rapid Temp Furnace”). The crystallized coating was crushed with ahammer into particles of −30+±mesh size (i.e., the fraction collectedbetween 600-micrometer opening size and 500-micrometer opening sizescreens). The particles were cleaned of debris by washing in a sonicbath (obtained from Cole-Parmer, Vernon Hills, Ill., under the tradedesignation “8891”) for 15 minutes, dried at 100° C., and several weremounted on a metal cylinder (3 cm in diameter and 2 cm high) usingcarbon tape. The mounted sample was sputter coated with a thin layer ofgold-palladium and viewed using a JEOL scanning electron microscopy(SEM) (Model JSM 840A). The fractured surface was rough and no crystalscoarser than 200 nanometers (nm) were observed (FIG. 5) in the SEM.

Example 23

Feed particles were made as described in Example 22 using the following50-gram mixture: 21.5 grams of alumina particles (obtained from AlcoaIndustrial Chemicals, Bauxite, Ark. under the trade designation“A16SG”), 9 grams of zirconium oxide particles (obtained from ZirconiaSales, Inc. of Marietta, Ga. under the trade designation “DK-2”), and19.5 grams of cerium oxide particles (obtained from Rhone-Poulence,France). The ratio of alumina to zirconia in the starting material was2.4:1 and the alumina and zirconia collectively made up about 61 weightpercent. Feed particles were flame-formed into beads (of a size thatvaried from a few micrometers up to 250 micrometers) as described inExample 22. Subsequently, the flame-formed beads having diametersbetween 180 micrometers and 250 micrometers were passed through a plasmagun and deposited on stainless and carbon steel substrates as describedin Example 22.

The 1080 carbon steel substrates were flexed, thus separating thecoating from the substrate resulting in a free-standing bulk material.The resulting bulk material had a z dimension (thickness) of about 700micrometers, as determined using optical microscopy. The microstructurewas also observed using optical microscopy. The material consisted ofgenerally spherical and oblique crystalline particles, which wereopaque, within a predominantly amorphous matrix, which was transparent.Amorphous material is typically transparent due to the lack of lightscattering centers such as crystal boundaries, while the crystallineparticles show a crystalline structure and are opaque due to lightscattering effects. The crystalline phases, determined by powder XRDanalysis as described in Example 22, consisted of Zr₀ ₄Ce₀ ₆O₂ (cubic)and transitional Al₂O₃.

A second deposition experiment was carried out using the flame-formedbeads having diameters less than 125 micrometers. The resulting coatinghad a z dimension (thickness) of about 1100 micrometers, as determinedusing optical microscopy. The microstructure was also observed usingoptical microscopy. This material had similar features (i.e., consistedof generally spherical and oblique crystalline particles within apredominantly amorphous matrix) to those of the material formed frombeads having diameters between 180 micrometers and 250 micrometers. Thecrystalline phases, determined by XRD analysis as described in Example22, consisted of Zr_(0.4)Ce₀ ₆O₂ (cubic) and transitional Al₂O₃.

The average hardness of the as-sprayed material of this example wasdetermined as follows. Sections of the material were mounted in mountingresin (obtained under the trade designation “TRANSOPTIC POWDER” fromBuehler, Lake Bluff, Ill.). The resulting cylinder of resin was about2.5 cm in diameter and about 1.9 cm high. The mounted section wasprepared using conventional polishing techniques using a polisher(obtained from Buehler, Lake Bluff, Ill. under the trade designation“ECOMET 3”). The sample was polished for about 3 minutes with a diamondwheel, followed by 5 minutes of polishing with each of 45, 30, 15, 9, 3,and 1-micrometer slurries. The microhardness measurements were madeusing a conventional microhardness tester (obtained under the tradedesignation “MITUTOYO MVK-VL” from Mitutoyo Corporation, Tokyo, Japan)fitted with a Vickers indenter using a 100-gram indent load. Themicrohardness measurements were made according to the guidelines statedin ASTM Test Method E384 Test Methods for Microhardness of Materials(1991), the disclosure of which is incorporated herein by reference. Theaverage microhardness (an average of 20 measurements) of the material ofthis example was 15 gigapascals (Gpa).

Example 24

Feed particles were made as described in Example 22 using the following50-gram mixture: 27.9 grams of alumina particles (obtained from AlcoaIndustrial Chemicals, Bauxite, Ark. under the trade designation“A16SG”), 7.8 grams of zirconium oxide particles (obtained from ZirconiaSales, Inc. of Marietta, Ga. under the trade designation “DK-2”), and14.3 grams of yttrium oxide particles (obtained from H. C. Stark Newton,Mass.). The ratio of alumina to zirconia of initial starting materialswas 3.5:1 and the alumina and zirconia collectively made up about 72weight percent. The feed particles were then screened through a 30-meshscreen (600-micrometer opening size) and heat-treated at 1400° C. for 2hours in an electrically heated furnace (obtained from CM Furnaces,Bloomfield, N.J. under the trade designation “Rapid Temp Furnace”). Theheat-treated particles were further screened to separate out particleswith diameters between 125 micrometers and 180 micrometers, which werethen passed through a plasma gun and deposited on stainless steelsubstrates as described in Example 22.

The 1080 carbon steel substrate was flexed, thus separating the coatingfrom the substrate resulting in a free-standing bulk material. Theresulting bulk material had a z dimension (thickness) of about 700micrometers, as determined using optical microscopy. The microstructurewas observed using optical microscopy. This material consisted ofgenerally crystalline opaque particles (which retained their originalshapes) within a predominantly transparent, amorphous matrix. Thecrystalline phases, determined by powder XRD analysis as described inExample 22, consisted of Al₅Y₃O₁₂ and Y_(0.15)Zr₀ ₈₅O_(1.93).

Another portion of the free-standing bulk material was crystallized at1300° C. for 1 hour and the fractured surface was sputter coated with athin layer of gold-palladium and viewed using a JEOL SEM (Model JSM840A), as described above in Example 22. The fractured surface was roughand no crystals coarser than 200 nm were observed (FIG. 6).

A second deposition experiment was carried out using heat-treatedparticles having diameters less than 125 micrometers. The resultingcoating was about 1500 micrometers thick (z dimension). Themicrostructure was observed using optical microscopy. This material hadsimilar features (consisted of generally opaque, crystalline particles(which retained their original shapes) within a predominantlytransparent, amorphous matrix) to the material formed from beads havingdiameters between 180 micrometers and 250 micrometers. The crystallinephases, determined by XRD analysis as described in Example 22, consistedof Al₅Y₃O₁₂ and Y_(0.15)Zr_(0.85)O_(1.93).

Example 25

A thick coating consisting of various layers of the above three exampleswas plasma sprayed using feed particles produced in Examples 22–24. Thefirst layer was coated as described in Example 23, the second asdescribed in Example 22, and the third as described in Example 24.

The substrate was not sandblasted prior to coating so that it wasremoved easily by plying it apart by hand, resulting in a free-standingbulk material, approximately 75 millimeters (mm)×25 mm×7.5 mm. Across-section, cutting through each layer, was sectioned from thematerial using a diamond saw. The sectioned piece was mounted inmounting resin (obtained under the trade designation “TRANSOPTIC POWDER”from Buehler, Lake Bluff, Ill.) such that the different layers werevisible. The resulting cylinder of resin was about 2.5 cm in diameterand about 1.9 cm tall (i.e., high). The mounted section was preparedusing conventional polishing techniques using a polisher (obtained fromBuehler, Lake Bluff, Ill. under the trade designation “ECOMET 3”). Thesample was polished for about 3 minutes with a diamond wheel, followedby 5 minutes of polishing with each of 45, 30, 15, 9, 3, and1-micrometer slurries.

The first layer had a z dimension (thickness) of approximately 2.5 mm,as determined using optical microscopy. The microstructure was observedusing optical microscopy. This material had similar features to those ofthe material of Example 23 (i.e., consisted of generally spherical andopaque crystalline particles within a predominantly transparent,amorphous matrix). The second layer had a z dimension (thickness) ofapproximately 2 mm, as determined using optical microscopy. Themicrostructure was also observed using optical microscopy. This materialhad similar features to those of the material of Example 22 (i.e., wastransparent suggesting it was amorphous). The third layer had a zdimension (thickness) of approximately 3 mm, as determined using opticalmicroscopy. The microstructure was also observed using opticalmicroscopy. This material had similar features to those of the materialof Example 24 (i.e., it consisted of generally opaque crystallineparticles (which retained their original shapes) within a predominantlytransparent, amorphous matrix).

Example 26

The consolidated material produced in Example 21 was crushed by using a“Chipmunk” jaw crusher (Type VD, manufactured by BICO Inc., Burbank,Calif.) into abrasive particles and graded to retain the −30+±meshfraction (i.e., the fraction collected between 600-micrometer openingsize and 500-micrometer opening size screens) and the −35+′mesh fraction(i.e., the fraction collected between 500-micrometer opening size and425-micrometer opening size screens). The two mesh fractions werecombined to provide a 50/50 blend.

An average aspect ratio of the particles was measured using a ZeissImage Analysis System (Zeiss Stemi SV11 microscope and software loadedon a computer) and a video camera (3 CCD camera, model 330, (obtainedfrom Dage MTI Inc., Michigan City, Ind.)). The resulting aspect ratiowas 1.86.

Density of the particles was measured using a gas pychometer AccuPyc1330, Micromeritics, Norcross, Ga. The resulting density was 4.65 gramsper cubic centimeter (g/cc).

The crushed particles were heat-treated at 1300° C. for 45 minutes in anelectrically heated furnace (obtained from CM Furnaces, Bloomfield, N.J.under the trade designation “Rapid Temp Furnace”). The resultingcrystalline particles retained their original crushed shape. The densityof the particle was found to be 5.24 grams per cubic centimeter (g/cc).The crystallized glass ceramic phases, determined by XRD analysis asdescribed in Examples 22, were composed of LaAlO₃, cubic/tetragonalZrO₂, LaAl₁₁O₁₈, α-Al₂O₃, monoclinic ZrO₂ and minor amorphous phases.

Example 27–28

A 250-ml polyethylene bottle (7.3-cm diameter) was charged with 19.3grams of alumina particles (obtained from Alcoa Industrial Chemicals,Bauxite, Ark., under the trade designation “A16SG”), 9.5 grams ofzirconium oxide particles (obtained from Zirconia Sales, Inc. ofMarietta, Ga. under the trade designation “DK-2”), and 21.2 grams oflanthanum oxide particles (obtained from Molycorp Inc., Mountain Pass,Calif.), 75 grams of isopropyl alcohol, and 200 grams of alumina millingmedia (cylindrical shape, both height and diameter of 0.635 cm; 99.9%alumina; obtained from Coors, Golden, Colo.). The contents of thepolyethylene bottle were milled for 16 hours at 60 revolutions perminute (rpm). After the milling, the milling media were removed and theslurry was poured onto a warm (approximately 75° C.) glass (“PYREX”)pan, where it dried within 3 minutes. The dried mixture was screenedthrough a 14-mesh screen (1400 micrometer opening size) with the aid ofa paint brush and pre-sintered at 1400° C., in air, for two hours.

A hole (approximately 13 mm in diameter, about 8 cm deep) was bored atthe end of a graphite rod (approximately 60 cm long, 15 mm in diameter).About 20 grams of pre-sintered particles were inserted into the hollowend. The hollow end of the graphite rod was inserted into the hot zoneof a resistively heated furnace (obtained from Astro Industries, SantaBarbara, Calif.). The furnace was modified to convert it into a tubefurnace with graphite tube with an inner diameter of approximately 18mm. The hot zone was maintained at a temperature of 2000° C. and thefurnace was tilted approximately 30° so that the melt would not spillout of the rod. The rod end was held in the hot zone for 10 minutes toensure uniform melting. After the ten minutes, the rod was quicklyremoved from the furnace and tilted to pour the melt onto a quenchingsurface.

For Example 27, the quenching surface was two opposing stainless steelplates. The plates, 17.8 cm×5 cm×2.5 cm, were placed on their long edgesparallel to each other with a gap of about 1 mm. The melt was pouredinto the gap where it rapidly solidified into a plate with a z dimension(thickness) of about 1 mm. The quenched melt was predominantlytransparent and amorphous and exhibited a glass transition (T_(g)) of885° C. and a crystallization temperature (T_(x)) of 930° C. asdetermine by a DTA trace obtained as described in Examples 1–20.

For Example 28, the quenching surface was two counter-rotating steelrollers. Rollers were 5 cm in diameter and driven by an electric motorat 80 rpm. The gap between the rollers was approximately 0.8 mm. Themelt was poured into the gap where the rollers rapidly solidified into aplate with significant x and y dimensions and a z dimension (thickness)of 0.8 mm. The quenched melt was predominantly transparent and amorphousand exhibited a glass transition (T_(g)) of 885° C. and acrystallization temperature (T_(x)) of 930° C., as determine by a DTAtrace obtained as described in Examples 1–20.

Example 29

The bulk amorphous/glass material produced in Example 21 was crushed byusing a “Chipmunk” jaw crusher (Type VD, manufactured by BICO Inc.,Burbank, Calif.) into abrasive particles and graded to retain the −30+35mesh fraction (i.e., the fraction collected between 600-micrometeropening size and 500-micrometer opening size screens) and the −35+40mesh fraction (i.e., the fraction collected between 500-micrometeropening size and 425-micrometer opening size screens). The two meshfractions were combined to provide a 50/50 blend.

An aspect ratio measurement was taken using the method described inExample 26. The resulting aspect ratio was 1.83.

Density of the particles was taken using the method described in Example26. The resulting density was 4.61 g/cc.

Examples 30–31

A hot-pressed disk was prepared as describe in Example 21 and wassectioned into 2 bars (approximately 2 cm×0.5 cm×0.5 cm) using a diamondsaw (obtained from Buehler, Lake Bluff, Ill. under the trade designation“ISOMET 1000”). Both bars were annealed in an electrically heatedfurnace (obtained from CM Furnaces, Bloomfield, N.J. under the tradedesignation “Rapid Temp Furnace”) at 800° C. for 2 hours. Nocrystallization occurred during the annealing process.

For Example 30, one bar was crushed with a hammer into particles of−30+35 mesh size (i.e., the fraction collected between 600-micrometeropening size and 500-micrometer opening size screens). The crushedparticles were heat-treated at 1300° C. for 1 hour in an electricallyheated furnace (obtained from CM Furnaces, Bloomfield, N.J. under thetrade designation “Rapid Temp Furnace”) to crystallize them. Theparticles were cleaned of debris by washing in a sonic bath (obtainedfrom Cole-Parmer, Vernon Hills, Ill., under the trade designation“8891”) for 15 minutes, dried at 100° C., and several were mounted on ametal cylinder (3 cm in diameter and 2 cm high) using carbon tape. Themounted sample was sputtered with a thin layer of gold-palladium andview using a JEOL SEM (Model JSM 840A).

Classic glass fracture characteristics were noticeable in the materialof Example 30, even after crystallization took place. The fracturesurface shown in FIG. 7 is a good example of Wallner lines, common inmost glass fracture. The fracture surface shown in FIG. 8 displayshackle, another common characteristic of glass fracture. The definitionsof Wallner lines and hackle are taken as those given in the textbook,Fundamentals of Inorganic Glasses, Arun K Varshneya, p. 425–27, 1994.

The average hardness of the material of Example 30 was determined asfollows. Several particles were mounted in mounting resin (obtainedunder the trade designation “TRANSOPTIC POWDER” from Buehler, LakeBluff, Ill.). The resulting cylinder of resin was about 2.5 cm indiameter and about 1.9 cm high. The mounted section was prepared usingconventional polishing techniques using a polisher (obtained fromBuehler, Lake Bluff, Ill. under the trade designation “ECOMET 3”). Thesample was polished for about 3 minutes with a diamond wheel, followedby 5 minutes of polishing with each of 45, 30, 15, 9, 3 and 1-micrometerslurries. The microhardness measurements were made using a conventionalmicrohardness tester (obtained under the trade designation “MITUTOYOMVK-VL” from Mitutoyo Corporation, Tokyo, Japan) fitted with a Vickersindenter using a 500-gram indent load. The microhardness measurementswere made according to the guidelines stated in ASTM Test Method E384Test Methods for Microhardness of Materials (1991), the disclosure ofwhich is incorporated herein by reference. The microhardness were anaverage of 20 measurements. The average microhardness of the material ofExample 30 was 16.4 GPa.

For Example 31, the second half of the bar was heat-treated at 1300° C.for 1 hour in an electrically heated furnace (obtained from CM Furnaces,Bloomfield, N.J. under the trade designation “Rapid Temp Furnace”). Theheat-treated bar was crushed with a hammer into particles of −30+35 meshsize (i.e., the fraction collected between 600-micrometer opening sizeand 500-micrometer opening size screens). The particles were mounted andviewed using above described methods.

In contrast to the glass-fractured surface of the material of Example30, the material of Example 31 exhibited fractured surfaces commonlyseen in polycrystalline material. The fractured surface shown in FIG. 9shows a rough surface with feature similar in size to the crystal size,typical of transgranular fracture.

Example 32

Beads from Example 4 were heat-treated at 1300° C. for 30 minutes in anelectrically heated furnace. The crystallized beads were mounted andpolished as described in Examples 30–31 and coated with a thin layer ofgold-palladium and view using a JEOL SEM (Model JSM 840A). FIG. 10 is atypical back-scattered electron (BSE) micrograph of the microstructurefound in crystallized beads. The crystallized sample was nanocrystallinewith very narrow distribution of crystal size, with no crystals beinglarger than 200 nm visually observed from the micrograph.

The average crystal size was determined by the line intercept methodaccording to the ASTM standard E 112-96 “Standard Test Methods forDetermining Average Grain Size”. The sample was mounted in mountingresin (obtained under the trade designation “TRANSOPTIC POWDER” fromBuehler, Lake Bluff, Ill.). The resulting cylinder of resin was about2.5 cm in diameter and about 1.9 cm high. The mounted section wasprepared using conventional polishing techniques using a polisher(obtained from Buehler, Lake Bluff, Ill. under the trade designation“ECOMET 3”). The sample was polished for about 3 minutes with a diamondwheel, followed by 5 minutes of polishing with each of 45, 30, 15, 9, 3,and 1-micrometer slurries. The mounted and polished sample was coatedwith a thin layer of gold-palladium and view using a JEOL SEM (Model JSM840A). A typical back-scattered electron (BSE) micrograph of themicrostructure found in the sample was used to determine the averagecrystal size as follows. The number of crystals that intersected perunit length (N_(L)) of a random line were drawn across the micrographwas counted. The average crystal size is determined from this numberusing the following equation.

${{Average}\mspace{14mu}{Crystal}\mspace{14mu}{Size}} = \frac{1.5}{N_{L}M}$

Where N_(L) is the number of crystals intersected per unit length and Mis the magnification of the micrograph. The average crystal size in thesample was 140 nm, as measured by line-intercept method.

Example 33

The consolidated material produced in Example 21 was heat treated at1300° C. for 45 minutes in an electrically heated furnace (obtained fromCM Furnaces, Bloomfield, N.J. under the trade designation “Rapid TempFurnace”). The resulting crystalline material was crushed by using a“Chipmunk” jaw crusher (Type VD, manufactured by BICO Inc., Burbank,Calif.) into abrasive particles and graded to retain the −30+35 fraction(i.e., the fraction collected between 600-micrometer opening size and500-micromter opening size screens) and the −35+40 mesh fraction (i.e.,the fraction collected 500-micrometer opening size and 5425-micrometeropening size screens). The two mesh fractions were combined to provide a50/50 blend.

An aspect ratio measurement was taken using the method of Example 26.The resulting aspect ratio was 1.84.

Density of the particles was taken using the method of Example 26. Theresulting density was 5.19 g/cc.

Example 34

About 150 grams of the beads prepared as described in Example 1 wereplaced in a 5 centimeter (cm)×5 cm×5 cm steel can, which was thenevacuated and sealed from the atmosphere. The steel can was subsequentlyhot-isostatically pressed (HIPed) using a HIP apparatus (obtained underthe trade designation “IPS Eagle-6”, American Isostatic Pressing, OH).The HIPing was carried out at 207 MPa (30 ksi) pressure in an argonatmosphere. The HIPing furnace was ramped up to 970° C. at 25° C./minuteand held at that temperature for 30 minutes. After the HIPing, the steelcan was cut and the charge material removed. It was observed that beadscoalesced into a chunk of transparent, glassy material. The DTA trace,conducted as described in Examples 1–20, exhibited a glass transition(T_(g)) of 879° C. and a crystallization temperature (T_(x)) of 931° C.

Example 35

A polyethylene bottle was charged with 27.5 grams of alumina particles(obtained under the trade designation “APA-0.5” from Condea Vista,Tucson, Ariz.), 22.5 grams of calcium oxide particles (obtained fromAlfa Aesar, Ward Hill, Mass.) and 90 grams of isopropyl alcohol. About200 grams of zirconia milling media (obtained from Tosoh ceramics,Division of Bound Brook, N.J., under “YTZ”designation) were added to thebottle, and the mixture was milled at 120 revolutions per minute (rpm)for 24 hours. After the milling, the milling media were removed and theslurry was poured onto a glass (“PYREX”) pan where it was dried using aheat-gun. The dried mixture was ground with a mortar and pestle andscreened through a 70-mesh screen (212-micrometer opening size).

After grinding and screening, some of the particles were fed into ahydrogen/oxygen torch flame. The torch used to melt the particles,thereby generating melted glass beads, was a Bethlehem bench burner PM2Dmodel B, obtained from Bethlehem Apparatus Co., Hellertown, Pa.,delivering hydrogen and oxygen at the following rates. For the innerring, the hydrogen flow rate was 8 standard liters per minute (SLPM) andthe oxygen flow rate was 3 SLPM. For the outer ring, the hydrogen flowrate was 23 (SLPM) and the oxygen flow rate was 9.8 SLPM. The dried andsized particles were fed directly into the torch flame, where they weremelted and transported to an inclined stainless steel surface(approximately 51 centimeters (cm) (20 inches) wide with the slope angleof 45 degrees) with cold water running over (approximately 8liters/minute) the surface to form amorphous beads.

Examples 36–39

Examples 36–39 glass beads were prepared as described in Example 35,except the raw materials and the amounts of raw materials used arelisted in Table 3, below, and the milling of the raw materials wascarried out in 90 (milliliters) ml of isopropyl alcohol with 200 gramsof the zirconia media (obtained from Tosoh Ceramics, Division of BoundBrook, N.J., under “YTZ” designation) at 120 rpm for 24 hours. Thesources of the raw materials used are listed in Table 4, below.

TABLE 3 Example Weight percent of components Batch amounts, g 36 CaO: 36CaO: 18 Al₂O₃: 44 Al₂O₃: 22 ZrO₂: 20 ZrO₂: 10 37 La₂O₃: 48 La₂O₃: 24Al₂O₃: 52 Al₂O₃: 26 38 La₂O₃: 40.9 La₂O₃: 20.45 Al₂O₃: 40.98 Al₂O₃:20.49 ZrO₂: 18.12 ZrO₂: 9.06 39 SrO: 22.95 SrO: 11.47 Al₂O₃: 62.05Al₂O₃: 31.25 ZrO₂: 15 ZrO₂: 7.5

TABLE 4 Raw Material Source Alumina particles (Al₂O₃) Obtained fromCondea Vista, Tucson, AZ under the trade designation “APA-0.5” Calciumoxide particles (CaO) Obtained from Alfa Aesar, Ward Hill, MA Lanthanumoxide particles Obtained from Molycorp Inc. (La₂O₃) Strontium oxideparticles Obtained from Alfa Aesar (SrO) Yttria-stabilized Obtained fromZirconia Sales, Inc. of zirconium oxide Marietta, GA under the tradedesignation particles (Y-PSZ) “HSY-3”

Various properties/characteristics of some of Examples 35–39 materialswere measured as follows. Powder X-ray diffraction (using an X-raydiffractometer (obtained under the trade designation “PHILLIPS XRG 3100”from PHILLIPS, Mahwah, N.J.) with copper K α1 radiation of 1.54050Angstrom) was used to qualitatively measure phases present in examplematerials. The presence of a broad diffused intensity peak was taken asan indication of the amorphous nature of a material. The existence ofboth a broad peak and well-defined peaks was taken as an indication ofexistence of crystalline matter within an amorphous matrix. Phasesdetected in various examples are reported in Table 5, below.

TABLE 5 Phases detected via Hot-pressing Example X-ray diffraction ColorT_(g), ° C. T_(x), ° C. temp, ° C. 35 Amorphous* Clear 850 987 985 36Amorphous* Clear 851 977 975 37 Amorphous* Clear 855 920 970 38Amorphous* Clear 839 932 965 39 Amorphous* Clear 875 934 975 *glass, asthe example has a T_(g)

For differential thermal analysis (DTA), a material was screened toretain glass beads within the 90–125 micrometer size range. DTA runswere made (using an instrument obtained from Netzsch Instruments, Selb,Germany under the trade designation “NETZSCH STA 409 DTA/TGA”). Theamount of each screened sample placed in a 100-microliter Al₂O₃ sampleholder was 400 milligrams. Each sample was heated in static air at arate of 10° C./minute from room temperature (about 25° C.) to 1200° C.

Referring to FIG. 11, line 345 is the plotted DTA data for the Example35 material. Referring to FIG. 11 line 345, the material exhibited anendothermic event at a temperature around 799° C., as evidenced by thedownward curve of line 375. It was believed that this event was due tothe glass transition (T_(g)) of the material. At about 875° C., anexothermic event was observed as evidenced by the sharp peak in line345. It was believed that this event was due to the crystallization(T_(x)) of the material. These T_(g) and T_(x) values for other examplesare reported in Table 5, above.

FIGS. 12–15 are the plotted DTA data for Examples 36–39, respectively.

For each of Examples 35–39, about 25 grams of the glass beads wereplaced in a graphite die and hot-pressed using uniaxial pressingapparatus (obtained under the trade designation “HP-50”, ThermalTechnology Inc., Brea, Calif.). The hot-pressing was carried out in anargon atmosphere and 13.8 megapascals (MPa) (2000 pounds per square inch(2 ksi)) pressure. The hot-pressing temperature at which appreciableglass flow occurred, as indicated by the displacement control unit ofthe hot pressing equipment described above, are reported for Examples35–39 in Table 5, above.

Examples 40–46

A polyethylene bottle was charged with the raw materials listed in Table6, below (with the sources of the raw materials listed in Table 7,below), with 90 ml of isopropyl alcohol. About 200 grams of the zirconiamilling media (obtained from Tosoh Ceramics, Division of Bound Brook,N.J., under the trade designation “YTZ”) were added to the bottle, andthe mixture was milled at 120 revolutions per minute (rpm) for 24 hours.After the milling, the milling media were removed and the slurry waspoured onto a glass (“PYREX”) pan where it was dried using a heat-gun.The dried mixture was ground with a mortar and pestle and screenedthrough a 70-mesh screen (212-micrometer opening size screen). Aftergrinding and screening, some of the particles were fed into ahydrogen/oxygen torch flame to form beads as described in Examples 1–20.

TABLE 6 Example Weight percent of components Batch amounts, g 40 Y₂O₃:28.08 Y₂O₃: 14.04 Al₂O₃: 58.48 Al₂O₃: 29.24 ZrO₂: 13.43 ZrO₂: 6.72 41Y₂O₃: 19 Y₂O₃: 9.5 Al₂O₃: 51 Al₂O₃: 25.5 ZrO₂: 17.9 ZrO₂: 8.95 La₂O₃:12.1 La₂O₃: 6.05 42 Y₂O₃: 19.3 Y₂O₃: 9.65 Al₂O₃: 50.5 Al₂O₃: 25.25 ZrO₂:17.8 ZrO₂: 8.9 Nd₂O₃: 12.4 Nd₂O₃: 6.2 43 Y₂O₃: 27.4 Y₂O₃: 13.7 Al₂O₃:50.3 Al₂O₃: 25.15 ZrO₂: 17.8 ZrO₂: 8.9 Li₂CO₃: 4.5 Li₂CO₃: 2.25 44 Y₂O₃:27.4 Y₂O₃: 13.7 Al₂O₃: 50.3 Al₂O₃: 25.15 ZrO₂: 17.8 ZrO₂: 8.9 CaO: 4.5CaO: 2.25 45 Y₂O₃: 27.4 Y₂O₃: 13.7 Al₂O₃: 50.3 Al₂O₃: 25.15 ZrO₂: 17.8ZrO₂: 8.9 NaHCO₃: 2.25 NaHCO₃: 2.25 46 Y₂O₃: 27.4 Y₂O₃: 13.7 Al₂O₃: 50.3Al₂O₃: 25.15 ZrO₂: 17.8 ZrO₂: 8.9 SiO₂: 2.25 SiO₂: 2.25

TABLE 7 Raw Material Source Alumina particles (Al₂O₃) Obtained fromCondea Vista, Tucson, AZ under the trade designation “APA-0.5” Calciumoxide particles (CaO) Obtained from Alfa Aesar, Ward Hill, MA Lanthanumoxide particles Obtained from Molycorp Inc., Mountain (La₂O₃) Pass, CALithium carbonate particles Obtained from Aldrich Chemical Co. (Li₂CO₃)Neodymium oxide particles Obtained from Molycorp Inc. (Nd₂O₃) Silicaparticles (SiO₂) Obtained from Alfa Aesar Sodium bicarbonate particlesObtained from Aldrich Chemical Co. (NaHCO₃) Yttria-stabilized Obtainedfrom Zirconia Sales, Inc. of zirconium oxide Marietta, GA under thetrade designation particles (Y-PSZ) “HSY-3”

Various properties/characteristics of some Example 40–46 materials weremeasured as follows. Powder X-ray diffraction (using an X-raydiffractometer (obtained under the trade designation “PHILLIPS XRG 3100”from Phillips, Mahwah, N.J.) with copper K α1 radiation of 1.54050Angstrom) was used to qualitatively measure phases present in examplematerials. The presence of a broad diffused intensity peak was taken asan indication of the amorphous nature of a material. The existence ofboth a broad peak and well-defined peaks was taken as an indication ofexistence of crystalline matter within an amorphous matrix. Phasesdetected in various examples are reported in Table 8, below.

TABLE 8 Exam- Phases detected via Hot-pressing ple X-ray diffractionColor T_(g), ° C. T_(x), ° C. temp, ° C. 40 Amorphous* and Clear/ 874932 980 Crystalline milky 41 Amorphous* Clear 843 938 970 42 Amorphous*Blue/ 848 934 970 pink 43 Amorphous* Clear 821 927 970 44 Amorphous*Clear 845 922 970 45 Amorphous* Clear 831 916 970 46 Amorphous* Clear826 926 970

For differential thermal analysis (DTA), a material was screened toretain beads in the 90–125 micrometer size range. DTA runs were made(using an instrument obtained from Netzsch Instruments, Selb, Germanyunder the trade designation “NETZSCH STA 409 DTA/TGA”). The amount ofeach screened sample placed in a 100-microliter Al₂O₃ sample holder was400 milligrams. Each sample was heated in static air at a rate of 10°C./minute from room temperature (about 25° C.) to 1200° C.

The hot-pressing temperature at which appreciable glass flow occurred,as indicated by the displacement control unit of the hot pressingequipment described above in Examples 36–39, are reported for variousexamples in Table 8, above.

Example 47

A polyurethane-lined mill was charged with 819.6 grams of aluminaparticles (“APA-0.5”), 818 grams of lanthanum oxide particles (obtainedfrom Molycorp, Inc.), 362.4 grams of yttria-stabilized zirconium oxideparticles (with a nominal composition of 94.6 wt-% ZrO₂ (+HfO₂) and 5.4wt-% Y₂O₃; obtained under the trade designation “HSY-3” from ZirconiaSales, Inc. of Marietta, Ga.), 1050 grams of distilled water and about2000 grams of zirconia milling media (obtained from Tosoh Ceramics,Division of Bound Brook, N.J., under the trade designation “YTZ”). Themixture was milled at 120 revolutions per minute (rpm) for 4 hours tothoroughly mix the ingredients. After the milling, the milling mediawere removed and the slurry was poured onto a glass (“PYREX”) pan whereit was dried using a heat-gun. The dried mixture was ground with amortar and pestle and screened through a 70-mesh screen (212-micrometeropening size). After grinding and screening, some of the particles werefed into a hydrogen/oxygen torch flame as described in Examples 1–20.

About 50 grams of the beads was placed in a graphite die and hot-pressedusing a uniaxial pressing apparatus (obtained under the tradedesignation “HP-50”, Thermal Technology Inc., Brea, Calif.). Thehot-pressing was carried out at 960° C. in an argon atmosphere and 13.8megapascals (MPa) (2000 pounds per square inch (2 ksi)) pressure. Theresulting translucent disk was about 48 millimeters in diameter, andabout 5 mm thick. Additional hot-press runs were performed to makeadditional disks. FIG. 16 is an optical photomicrograph of a sectionedbar (2-mm thick) of the hot-pressed material demonstrating itstransparency.

The density of the resulting hot-pressed glass material was measuredusing Archimedes method, and found to be within a range of about 4.1–4.4g/cm³. The Youngs' modulus (E) of the resulting hot-pressed glassmaterial was measured using a ultrasonic test system (obtained fromNortek, Richland, Wash. under the trade designation “NDT-140”), andfound to be within a range of about 130–150 GPa.

The average microhardnesses of the resulting hot-pressed material wasdetermined as follows. Pieces of the hot-pressed material (about 2–5millimiters in size) were mounted in mounting resin (obtained under thetrade designation “ECOMET 3” from Buehler Ltd., Lake Bluff, Ill.). Theresulting cylinder of resin was about 2.5 cm (1 inch) in diameter andabout 1.9 cm (0.75 inch) tall (i.e., high). The mounted samples werepolished using a conventional grinder/polisher (obtained under the tradedesignation “ECOMET 3” from Buehler Ltd.) and conventional diamondslurries with the final polishing step using a 1-micrometer diamondslurry (obtained under the trade designation “METADI” from Buehler Ltd.)to obtain polished cross-sections of the sample.

The microhardness measurements were made using a conventionalmicrohardness tester (obtained under the trade designation “MITUTOYOMVK-VL” from Mitutoyo Corporation, Tokyo, Japan) fitted with a Vickersindenter using a 500-gram indent load. The microhardness measurementswere made according to the guidelines stated in ASTM Test Method E384Test Methods for Microhardness of Materials (1991), the disclosure ofwhich is incorporated herein by reference. The microhardness values werean average of 20 measurements. The average microhardness of thehot-pressed material was about 8.3 GPa.

The average indentation toughness of the hot-pressed material wascalculated by measuring the crack lengths extending from the apices ofthe vickers indents made using a 500 gram load with a microhardnesstester (obtained under the trade designation “MITUTOYO MVK-VL” fromMitutoyo Corporation, Tokyo, Japan). Indentation toughness (K_(IC)) wascalculated according to the equation:K _(IC)=0.016 (E/H)^(1/2)(P/c)^(3/2)wherein: E=Young's Modulus of the material;

-   -   H=Vickers hardness;    -   P=Newtons of force on the indenter;    -   c=Length of the crack from the center of the indent to its end.

Samples for the toughness were prepared as described above for themicrohardness test. The reported indentation toughness values are anaverage of 5 measurements. Crack (c) were measured with a digitalcaliper on photomicrographs taken using a scanning electron microscope(“JEOL SEM” (Model JSM 6400)). The average indentation toughness of thehot-pressed material was 1.4 MPa·m^(1/2).

The thermal expansion coefficient of the hot-pressed material wasmeasured using a thermal analyser (obtained from Perkin Elmer, Shelton,Conn., under the trade designation “PERKIN ELMER THERMAL ANALYSER”). Theaverage thermal expansion coefficient was 7.6×10⁻⁶/° C.

The thermal conductivity of the hot-pressed material was measuredaccording to an ASTM standard “D 5470-95, Test Method A” (1995), thedisclosure of which is incorporated herein by reference. The averagethermal conductivity was 1.15 W/m*K.

The translucent disk of hot-pressed La₂O₃—Al₂O₃—ZrO₂ glass washeat-treated in a furnace (an electrically heated furnace (obtainedunder the trade designation “Model KKSK-666-3100” from Keith Furnaces ofPico Rivera, Calif.)) as follows. The disk was first heated from roomtemperature (about 25° C.) to about 900° C. at a rate of about 10°C./min and then held at 900° C. for about 1 hour. Next, the disk washeated from about 900° C. to about 1300° C. at a rate of about 10°C./min and then held at 1300° C. for about 1 hour, before cooling backto room temperature by turning off the furnace. Additional runs wereperformed with the same heat-treatment schedule to make additionaldisks.

FIG. 17 is a scanning electron microscope (SEM) photomicrograph of apolished section of heat-treated Example 47 material showing the finecrystalline nature of the material. The polished section was preparedusing conventional mounting and polishing techniques. Polishing was doneusing a polisher (obtained from Buehler of Lake Bluff, Ill. under thetrade designation “ECOMET 3 TYPE POLISHER-GRINDER”). The sample waspolished for about 3 minutes with a diamond wheel, followed by threeminutes of polishing with each of 45, 30, 15, 9, and 3-micrometerdiamond slurries. The polished sample was coated with a thin layer ofgold-palladium and viewed using JEOL SEM (Model JSM 840A).

Based on powder X-ray diffraction as described in Example 22 of aportion of heat-treated Example 47 material and examination of thepolished sample using SEM in the backscattered mode, it is believed thatthe dark portions in the photomicrograph were crystalline LaAl₁₁O₁₈, thegray portions crystalline LaAlO₃, and the white portions crystallinecubic/tetragonal ZrO₂.

The density of the heat-treated material was measured using Archimedesmethod, and found to be about 5.18 g/cm³. The Youngs' modulus (E) of theheat-treated material was measured using an ultrasonic test system(obtained from Nortek, Richiand, Wash. under the trade designation“NDT-140”), and found to be about 260 GPa. The average microhardness ofthe heat-treated material was determined as described above for theExample 47 glass beads, and was found to be 18.3 GPa. The averagefracture toughness (K_(ic)) of the heat-treated material was determinedas described above for the Example 47 hot-pressed material, and wasfound to be 3.3 MPa·m^(1/2).

Examples 48–62

Examples 48–62 beads were prepared as described in Example 47, exceptthe raw materials and the amounts of raw materials, used are listed inTable 9, below, and the milling of the raw materials was carried out in90 milliliters (ml) of isopropyl alcohol with 200 grams of the zirconiamedia (obtained from Tosoh Ceramics, Division of Bound Brook, N.J.,under the trade designation “YTZ”) at 120 rpm for 24 hours. The sourcesof the raw materials used are listed in Table 10, below.

TABLE 9 Example Weight percent of components Batch amounts, g 48 La₂O₃:36.74 La₂O₃: 18.37 Al₂O₃: 46.98 Al₂O₃: 23.49 ZrO₂: 16.28 ZrO₂: 8.14 49La₂O₃: 35.35 La₂O₃: 17.68 Al₂O₃: 48.98 Al₂O₃: 24.49 ZrO₂: 15.66 ZrO₂:7.83 50 Al₂O₃: 41.0 Al₂O₃: 20.5 ZrO₂: 17.0 ZrO₂: 8.5 Eu₂O₃: 41.0 Eu₂O₃:20.5 51 Al₂O₃: 41.0 Al₂O₃: 20.5 ZrO₂: 18.0 ZrO₂: 9.0 Gd₂O₃: 41.0 Gd₂O₃:20.5 52 Al₂O₃: 41.0 Al₂O₃: 20.5 ZrO₂: 18.0 ZrO₂: 9.0 Dy₂O₃: 41.0 Dy₂O₃:20.5 53 La₂O₃: 35.0 La₂O₃: 17.5 Al₂O₃: 40.98 Al₂O₃: 20.49 ZrO₂: 18.12ZrO₂: 9.06 Nd₂O₃: 5.0 Nd₂O₃: 2.50 54 La₂O₃: 35.0 La₂O₃: 17.5 Al₂O₃:40.98 Al₂O₃: 20.49 ZrO₂: 18.12 ZrO₂: 9.06 CeO₂: 5.0 CeO₂: 2.50 55 La₂O₃:41.7 La₂O₃: 20.85 Al₂O₃: 35.4 Al₂O₃: 17.7 ZrO₂: 16.9 ZrO₂: 8.45 MgO: 6.0MgO: 3.0 56 La₂O₃: 43.02 La₂O₃: 21.51 Al₂O₃: 36.5 Al₂O₃: 18.25 ZrO₂:17.46 ZrO₂: 8.73 Li₂CO₃: 3.0 Li₂CO₃: 1.50 57 La₂O₃: 41.7 La₂O₃: 20.85Al₂O₃: 35.4 Al₂O₃: 17.70 ZrO₂: 16.9 ZrO₂: 8.45 Li₂CO₃: 6.0 Li₂CO₃: 3.0058 La₂O₃: 38.8 La₂O₃: 19.4 Al₂O₃: 40.7 Al₂O₃: 20.35 ZrO₂: 17.5 ZrO₂:8.75 Li₂CO₃: 3 Li₂CO₃: 1.50 59 La₂O₃: 43.02 La₂O₃: 21.51 Al₂O₃: 36.5Al₂O₃: 18.25 ZrO₂: 17.46 ZrO₂: 8.73 TiO₂: 3 TiO₂: 1.50 60 La₂O₃: 43.02La₂O₃: 21.51 Al₂O₃: 36.5 Al₂O₃: 18.25 ZrO₂: 17.46 ZrO₂: 8.73 NaHCO₃: 3.0NaHCO₃: 1.50 61 La₂O₃: 42.36 La₂O₃: 21.18 Al₂O₃: 35.94 Al₂O₃: 17.97ZrO₂: 17.19 ZrO₂: 8.60 NaHCO₃: 4.5 NaHCO₃: 2.25 62 La₂O₃: 43.02 La₂O₃:21.51 Al₂O₃: 36.5 Al₂O₃: 18.25 ZrO₂: 17.46 ZrO₂: 8.73 MgO: 1.5 MgO: 0.75NaHCO₃: 1.5 NaHCO₃: 0.75 TiO₂: 1.5 TiO₂: 0.75

TABLE 10 Raw Material Source Alumina particles (Al₂O₃) Obtained fromCondea Vista, Tucson, AZ under the trade designation “APA-0.5” Ceriumoxide particles (CeO₂) Obtained from Rhone-Poulenc, France Europiumoxide particles Obtained from Aldrich Chemical Co. (Eu₂O₃) Gadoliniumoxide particles Obtained from Molycorp Inc., Mountain (Gd₂O₃) Pass, CAHafnium oxide particles Obtained from Teledyne Wah Chang (HfO₂) AlbanyCo., Albany, OR Lanthanum oxide particles Obtained from Molycorp Inc.(La₂O₃) Lithium carbonate particles Obtained from Aldrich Chemical Co.(Li₂CO₃) Magnesium oxide particles Obtained from Aldrich Chemical Co.(MgO) Neodymium oxide particles Obtained from Molycorp Inc. (Nd₂O₃)Sodium bicarbonate particles Obtained from Aldrich Chemical Co. (NaHCO₃)Titanium dioxide particles Obtained from Kemira Inc., (TiO₂) Savannah,GA Yttria-stabilized zirconium Obtained from Zirconia Sales, Inc. ofoxide particles (Y-PSZ) Marietta, GA under the trade designation “HSY-3”

Various properties/characteristics of some Example 47–62 materials weremeasured as follows. Powder X-ray diffraction (using an X-raydiffractometer (obtained under the trade designation “PHILLIPS XRG 3100”from PHILLIPS, Mahwah, N.J.) with copper K <1 radiation of 1.54050Angstrom) was used to qualitatively measure phases present in examplematerials. The presence of a broad diffused intensity peak was taken asan indication of the glassy nature of a material. The existence of botha broad peak and well-defined peaks was taken as an indication ofexistence of crystalline matter within a glassy matrix. Phases detectedin various examples are reported in Table 11, below.

TABLE 11 Phases detected Hot- via X-ray pressing Example diffractionColor T_(g), ° C. T_(x), ° C. temp, ° C. 47 Amorphous* Clear 834 932 96048 Amorphous* Clear 848 920 960 49 Amorphous* Clear 856 918 960 50Amorphous* Intense 874 921 975 yellow/ mustard 51 Amorphous* Clear 886933 985 52 Amorphous* Greenish 881 935 985 53 Amorphous* Blue/pink 836930 965 54 Amorphous* Yellow 831 934 965 55 Amorphous* Clear 795 901 95056 Amorphous* Clear 816 942 950 57 Amorphous* Clear 809 934 950 58Amorphous* Clear/ 840 922 950 greenish 59 Amorphous* Clear 836 934 95060 Amorphous* Clear 832 943 950 61 Amorphous* Clear 830 943 950 62Amorphous* Clear/some 818 931 950 green *glass, as the example has aT_(g)

For differential thermal analysis (DTA), a material was screened toretain beads in the 90–125 micrometer size range. DTA runs were made(using an instrument obtained from Netzsch Instruments, Selb, Germanyunder the trade designation “NETZSCH STA 409 DTA/TGA”). The amount ofeach screened sample placed in a 100-microliter Al₂O₃ sample holder was400 milligrams. Each sample was heated in static air at a rate of 10°C./minute from room temperature (about 25° C.) to 1200° C.

Referring to FIG. 18, line 801 is the plotted DTA data for the Example47 material. Referring to FIG. 18 line 801, the material exhibited anendothermic event at temperature around 840° C., as evidenced by thedownward curve of line 801. It was believed that this event was due tothe glass transition (T_(g)) of the material. At about 934° C., anexothermic event was observed as evidenced by the sharp peak in line801. It was believed that this event was due to the crystallization(T_(x)) of the material. These T_(g) and T_(x) values for other examplesare reported in Table 11, above.

The hot-pressing temperature at which appreciable glass flow occurred,as indicated by the displacement control unit of the hot pressingequipment described above, are reported for various examples in Table11, above.

Example 63

A polyethylene bottle was charged with 20.49 grams of alumina particles(“APA-0.5”), 20.45 grams of lanthanum oxide particles (obtained fromMolycorp, Inc.), 9.06 grams of yttria-stabilized zirconium oxideparticles (with a nominal composition of 94.6 wt-% ZrO₂ (+HfO₂) and 5.4wt-% Y₂O₃; obtained under the trade designation “HSY-3” from ZirconiaSales, Inc. of Marietta, Ga.), and 80 grams of distilled water. About450 grams of alumina milling media (10 mm diameter; 99.9% alumina;obtained from Union Process, Akron, Ohio) were added to the bottle, andthe mixture was milled at 120 revolutions per minute (rpm) for 4 hoursto thoroughly mix the ingredients. After the milling, the milling mediawere removed and the slurry was poured onto a glass (“PYREX”) pan whereit was dried using a heat-gun. The dried mixture was ground with amortar and pestle and screened through a 70-mesh screen (212-micrometeropening size).

A small quantity of the dried particles was melted in an arc dischargefurnace (Model No. 5T/A 39420; from Centorr Vacuum Industries, Nashua,N.H.). About 1 gram of the dried and sized particles was placed on achilled copper plate located inside the furnace chamber. The furnacechamber was evacuated and then backfilled with Argon gas at 13.8kilopascals (kPa) (2 pounds per square inch (psi)) pressure. An arc wasstruck between an electrode and a plate. The temperatures generated bythe arc discharge were high enough to quickly melt the dried and sizedparticles. After melting was complete, the material was maintained in amolten state for about 10 seconds to homogenize the melt. The resultantmelt was rapidly cooled by shutting off the arc and allowing the melt tocool on its own. Rapid cooling was ensured by the small mass of thesample and the large heat sinking capability of the water chilled copperplate. The fused material was removed from the furnace within one minuteafter the power to the furnace was turned off. Although not wanting tobe bound by theory, it is estimated that the cooling rate of the melt onthe surface of the water chilled copper plate was above 100° C./second.The fused material were transparent glass beads (largest diameter of abead was measured at 2.8 millimeters (mm)).

The resulting amorphous beads were placed in a poyethylene bottle (as inExample 1) together with 200 grams of 2-mm zirconia milling media(obtained from Tosoh Ceramics Bound Brook, N.J. under the tradedesignation “YTZ”). Three hundred grams of distilled water was added tothe bottle, and the mixture milled for 24 hours at 120 rpm to pulverizebeads into powder. The milled material was dried using a heat gun.Fifteen grams of the dried particles were placed in a graphite die andhot-pressed at 960° C. as described in Examples 21. The resulting diskwas translucent.

Example 64

Example 64 fused amorphous beads were prepared as described in Example63. About 15 grams of the beads were hot pressed as described in Example50except the bottom punch of the graphite die had 2 mm deep grooves. Theresulting material replicated the grooves, indicating very goodflowability of the glass during the heating under the applied pressure.

Comparative Example A

Comparative Example A fused material was prepared as described inExample 63, except the polyethylene bottle was charged with 27 grams ofalumina particles (“APA-0.5”), 23 grams of yttria-stabilized zirconiumoxide particles (with a nominal composition of 94.6 wt-% ZrO₂ (+HfO₂)and 5.4 wt-% Y₂O₃; obtained under the trade designation “HSY-3” fromZirconia Sales, Inc. of Marietta, Ga.) and 80 grams of distilled water.The composition of this example corresponds to a eutectic composition inthe Al₂O₃—ZrO₂ binary system. The resulting 100–150 micrometers diameterspheres were partially amorphous, with significant portions ofcrystallinity as evidenced by X-ray diffraction analysis.

Example 65

A sample (31.25 grams) of amorphous beads prepared as described inExample 47, and 18.75 grams of beads prepared as described inComparative Example A, were placed in a polyethylene bottle. After 80grams of distilled water and 300 grams of zirconia milling media (TosohCeramics, Bound Brook, N.J. under the trade designation “YTZ”) wereadded to the bottle, the mixture was milled for 24 hours at 120 rpm. Themilled material was dried using a heat gun. Twenty grams of the driedparticles were hot-pressed as described in Example 32. An SEMphotomicrograph of a polished section (prepared as described in Example47) of Example 65 material is shown in FIG. 19. The absence of crackingat interfaces between the Comparative Example A material (dark areas)and the Example 65 material (light areas) indicates the establishment ofgood bonding.

Grinding Performance of Examples 47 and 47A and Comparative Examples B–D

Example 47 hot-pressed material was crushed by using a “Chipmunk” jawcrusher (Type VD, manufactured by BICO Inc., Burbank, Calif.) into(abrasive) particles and graded to retain the −25+30 mesh fraction(i.e., the fraction collected between 25-micrometer opening and30-micrometer opening size sieves) and −30+35 mesh fractions (i.e., thefraction collected between 30-micrometer opening size and 35-micrometeropening size sieves) (USA Standard Testing Sieves). These two meshfractions were combined to provide a 50/50 blend. The blended materialwas heat treated as described in Example 47. Thirty grams of theresulting glass-ceramic abrasive particles were incorporated into acoated abrasive disc. The coated abrasive disc was made according toconventional procedures. The glass-ceramic abrasive particles werebonded to 17.8 cm diameter, 0.8 mm thick vulcanized fiber backings(having a 2.2 cm diameter center hole) using a conventional calciumcarbonate-filled phenolic make resin (48% resole phenolic resin, 52%calcium carbonate, diluted to 81% solids with water and glycol ether)and a conventional cryolite-filled phenolic size resin (32% resolephenolic resin, 2% iron oxide, 66% cryolite, diluted to 78% solids withwater and glycol ether). The wet make resin weight was about 185 g/m².Immediately after the make coat was applied, the glass-ceramic abrasiveparticles were electrostatically coated. The make resin was precured for120 minutes at 88° C. Then the cryolite-filled phenolic size coat wascoated over the make coat and abrasive particles. The wet size weightwas about 850 g/m². The size resin was cured for 12 hours at 99° C. Thecoated abrasive disc was flexed prior to testing.

Example 47A coated abrasive disk was prepared as described for Example47 except the Example 47A abrasive particles were obtained by crushing ahot-pressed and heat-treated Example 47 material, rather than crushingthen heat-treating.

Comparative Example B coated abrasive disks were prepared as describedfor Example 47 (above), except heat-treated fused alumina abrasiveparticles (obtained under the trade designation “ALODUR BFRPL”” fromTriebacher, Villach, Austria) was used in place of the Example 47glass-ceramic abrasive particles.

Comparative Example C coated abrasive discs were prepared as describedfor Example 47 (above), except alumina-zirconia abrasive particles(having a eutectic composition of 53% Al₂O₃ and 47% ZrO₂; obtained underthe trade designation “NORZON” from Norton Company, Worcester, Mass.)were used in place of the Example 47 glass-ceramic abrasive particles.

Comparative Example D coated abrasive discs were prepared as describedabove except sol-gel-derived abrasive particles (marketed under thetrade designation “321 CUBITRON” from the 3M Company, St. Paul, Minn.)was used in place of the Example 47 glass-ceramic abrasive particles.

The grinding performance of Example 47 and Comparative Examples B–Dcoated abrasive discs were evaluated as follows. Each coated abrasivedisc was mounted on a beveled aluminum back-up pad, and used to grindthe face of a pre-weighed 1.25 cm×18 cm×10 cm 1018 mild steel workpiece.The disc was driven at 5,000 rpm while the portion of the discoverlaying the beveled edge of the back-up pad contacted the workpieceat a load of 8.6 kilograms. Each disc was used to grind an individualworkpiece in sequence for one-minute intervals. The total cut was thesum of the amount of material removed from the workpieces throughout thetest period. The total cut by each sample after 12 minutes of grindingas well as the cut at the 12th minute (i.e., the final cut) are reportedin Table 12, below. The Example 47 results are an average of two discs,where as one disk was tested for each of Example 47A, and ComparativeExamples B, C, and D.

TABLE 12 Example Total cut, g Final cut, g 47 1163 92 47A 1197 92 Comp.B 514 28 Comp. C 689 53 Comp. D 1067 89

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

1. Amorphous material comprising at least 35 percent by weight Al₂O₃,based on the total weight of the amorphous material, and a metal oxideother than Al₂O₃, wherein the amorphous material contains not more than10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂,and V₂O₅, based on the total weight of the amorphous material, whereinthe amorphous material lacks any long range crystal structure asdetermined by X-ray diffraction, wherein the amorphous material has x,y, and z dimensions each perpendicular to each other, wherein each ofthe x, y, and z dimensions is at least 5 mm, and wherein the amorphousmaterial has a density of at least 85 percent of theoretical, with theproviso that if the metal oxide other than Al₂O₃ is CaO or ZrO₂, thenthe amorphous material further comprises a metal oxide other than Al₂O₃,CaO, and ZrO₂ at least a portion of which forms a distinct crystallinephase when the amorphous material is crystallized, and if the metaloxide other than Al₂O₃ is CaO, then the CaO is present up to 10 percentby weight, based on the total weight of the amorphous material.
 2. Theamorphous material according to claim 1 wherein the amorphous materialdoes not have a T_(g).
 3. An article comprising the amorphous materialaccording to claim
 1. 4. The amorphous material according to claim 1 inthe form of an IR window.
 5. Glass comprising at least 35 percent byweight Al₂O₃, based on the total weight of the glass, and a metal oxideother than Al₂O₃, wherein the glass contains not more than 10 percent byweight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, basedon the total weight of the glass, wherein the glass has x, y, and zdimensions each perpendicular to each other, and wherein each of the x,y, and z dimensions is at least 5 mm, with the proviso that if the metaloxide other than Al₂O₃ is CaO, then the glass further comprises a metaloxide other than Al₂O₃ or CaO at least a portion of which forms adistinct crystalline phase when the glass is crystallized, and if themetal oxide other than Al₂O₃ is CaO, then the CaO is present up to 10percent by weight, based on the total weight of the glass.
 6. The glassaccording to claim 5 in the form of an IR window.
 7. A method for makingglass-ceramic, the method comprising: heat-treating amorphous materialsuch that at least a portion of the amorphous material is converted to aglass-ceramic, the amorphous material comprising at least 35 percent byweight Al₂O₃, based on the total weight of the amorphous material, and ametal oxide other than Al₂O₃, wherein the amorphous material containsnot more than 10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the amorphousmaterial, wherein the amorphous material lacks any long range crystalstructure as determined by X-ray diffraction, wherein the amorphousmaterial has x, y, and z dimensions each perpendicular to each other,wherein each of the x, y, and z dimensions is at least 5 mm, and whereinthe amorphous material has a density of at least 85 percent oftheoretical, with the proviso that if the metal oxide other than Al₂O₃is CaO or ZrO₂, then the amorphous material further comprises a mutaloxide other than Al₂O₃, CaO, and ZrO₂ at least a portion of which formsa distinct crystalline phase when the amorphous material iscrystallized, and if the metal oxide other than Al₂O₃ is CaO, then theCaO is present up to 10 percent by weight, based on the total weight ofthe amorphous material.
 8. A method for making glass-ceramic, the methodcomprising: heat-treating glass such that at least a portion of theglass is converted to a glass-ceramic, the glass comprising at least 35percent by weight Al₂O₃, based on the total weight of the glass, and ametal oxide other than Al₂O₃, wherein the glass contains not more than10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂,and V₂O₅, based on the total weight of the glass, wherein the glass hasx, y, and z dimensions each perpendicular to each other, and whereineach of the x, y, and z dmensions is at least 5 mm, with the provisothat if the metal oxide other than Al₂O₃ is CaO, then the glass furthercomprises a metal oxide other than Al₂O₃ or CaO at least a portion ofwhich forms a distinct crystalline phase when the glass is crystallized,and if the metal oxide other than Al₂O₃ is CaO, then the CaO is presentup to 10 percent by weight, based on the total weight of the glass.
 9. Amethod for making abrasive particles, the method comprising:heat-treating amorphous material such that at least a portion of theamorphous material is converted to a glass-ceramic, the amorphousmaterial comprising at least 35 pcreent by weight Al₂O₃, based on thetotal weight of the amorphous material, and a metal oxide other thanAl₂O₃, wherein the amorphous material contains not more than 10 percentby weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅,based on the total weight of the amorphous material, wherein theamorphous material lacks any long range crystal structure as determinedby X-ray diffraction, wherein the amorphous material has x, y, and zdimensions each perpendicular to each other, wherein each of the x, y,and z dimensions is at least 5 mm, and wherein the amorphous materialhas a density of at least 85 percent of theoretical, with the provisothat if the metal oxide other than Al₂O₃ is CaO or ZrO₂, then theamorphous material further comprises a metal oxide other than Al₂O₃,CaO, and ZrO₂ at least a portion of which forms a distinct crystallinephase when the amorphous material is crystallized, and if the metaloxide other than Al₂O₃ is CaO, then the CaO is present up to 10 percentby weight, based on the total weight of the amorphous material; andcrushing the glass-ceramic to provide abrasive particles comprisingglass-ceramic.
 10. A method for making abrasive particles, the methodcomprising: heat-treating amorphous material such that at least aportion of the amorphous material is converted to a glass-ceramic, theamorphous material comprising at least 35 percent by weight Al₂O₃, basedon the total weight of the amorphous material, and a metal oxide otherthan Al₂O₃, wherein the amorphous material contains not more than 10percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, andV₂O₅, based on the total weight of the amorphous material, wherein theamorphous material lacks any long range crystal structure as determinedby X-ray diffraction, wherein the amorphous material has x, y, and zdimensions each perpendicular to each other, wherein each of the x, y,and z dimensions is at least 5 mm, and wherein the amorphous materialhas a density of at least 85 percent of theoretical, with the provisothat if the metal oxide other than Al₂O₃ is CaO, then the amorphousmaterial further comprises a metal oxide other than Al₂O₃ or CaO atleast a portion of which forms a distinct crystalline phase when theamorphous material is crystallized, and if the metal oxide other thanAl₂O₃ is CaO, then the CaO is present up to 10 percent by weight, basedon the total weight of the amorphous material; and crushing theglass-ceramic to provide abrasive particles comprising theglass-ceramic.
 11. A method for making abrasive particles, the methodcomprising: heat-treating particles comprising amorphous material suchthat at least a portion of the amorphous material is converted to aglass-ceramic, the amorphous material comprising at least 35 percent byweight Al₂O₃, based on the total weight of the amorphous material ofeach particle,. and a metal oxide other than Al₂O₃, wherein theamorphous material contains not more than 10 percent by weightcollectively As2O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thetotal weight of the amorphous material of each particle, wherein theamorphous material lacks any long range crystal structure as determinedby X-ray diffraction, wherein the amorphous material has x, y, and zdimensions each perpendicular to each other, wherein each of the x, y,and z dimensions is at least 5 mm, and wherein the amorphous materialhas a density of at least 85 percent of theoretical, with the provisothat if the metal oxide other than Al₂O₃, is CaO or ZrO₂, then theamorphous material further comprises a metal oxide other than Al₂O₃,CaO, and ZrO₂ at least a portion of which forms a distinct crystallinephase when the amorphous material is crystallized, and if the metaloxide other than Al₂O₃ is CaO, then the CaO is present up to 10 percentby weight, based on the total weight of the amorphous material.
 12. Amethod for making abrasive particles, the method comprising:heat-treating particles comprising glass such that at least a portion ofthe glass is converted to a glass-ceramic, the glass comprising at least35 percent by weight Al₂O₃, based on the total weight of the glass ofeach particle, and a metal oxide other than Al₂O₃, wherein the glasscontains not more than 10 percent by weight collectively As₂O₃, B₂O₃,GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of the glassof each particle, wherein the glass has x, y, and z dimensions eachperpendicular to each other, and wherein each of the x, y, and zdimensions is at least 5 mm, with the proviso that if the metal oxideother than Al₂O₃ is CaO, then the glass further comprises a metal oxideother than Al₂O₃ or CaO at least a portion of which forms a distinctcrystalline phase when the glass is crystallized, and if the metal oxideother than Al₂O₃ is CaO, then the CaO is present up to 10 percent byweight, based on the total weight of the glass.
 13. The method accordingto claim 12 wherein prior to the heat-treating the particles comprisingglass, a plurality of particles having a specified nominal grade isprovided, wherein at least a portion of the particles is a plurality ofthe particles comprising glass, and wherein the heat-treating isconducted such that a plurality of abrasive particles having a specifiednominal grade is provided, wherein at least a portion of the abrasiveparticles is a plurality of the glass-ceramic abrasive particles. 14.The method according to claim 12 further comprising grading theglass-ceramic abrasive particles to provide a plurality of abrasiveparticles having a specified nominal grade, wherein at least a portionof the plurality of abrasive particles is a plurality of theglass-ceramic abrasive particles.
 15. A method for making an articlecomprising glass comprising at least 35 percent by weight Al₂O₃, basedon the total weight at the glass, and a metal oxide other than Al₂O₃,wherein the glass contains not more than 10 percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, P₂O₅, TeO₂, and V₂O₅, basedon the total weight of the glass, the method comprising: providing glassparticles comprising at least 35 percent by weight Al₂O₃, based on thetotal weight of the glass, and a metal oxide other than Al₂O₃, whereinthe glass contains not more than 10 percent by weight As₂O₃, B₂O₃, GeO₂,P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of the glass, theglass having a T_(g); heating the glass particles above the T_(g) suchthat the glass particles coalesce to form a shape; and cooling the shapeto provide the article, with the proviso that if the metal oxide otherthan Al₂O₃ is CaO, then the glass further comprises a metal oxide otherthan Al₂O₃ or CaO at least a portion of which forms a distinctcrystalline phase when the glass is crystallized.
 16. A method formaking glass particles, the method comprising: atomizing a glass meltcomprising at least 35 percent by weight Al₂O₃, based on the totalweight of the glass melt, and a metal oxide other than Al₂O₃, whereinthe glass melt contains not more than 10 percent by weight collectivelyAs₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weightof the glass melt; and cooling the atomized glass melt to provide glassparticles comprising at least 35 percent by weight Al₂O₃, based on thetotal weight of each glass particle, and a metal oxide other than Al₂O₃,wherein each glass particle contains not more than 10 percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thetotal weight of each glass particle, wherein the glass has x, y, and zdimensions each perpendicular to each other, and wherein each of the x,y, and z dimensions is at least 5 mm, with the proviso that if the metaloxide other than Al₂O₃ is CaO, then the glass further comprises a metaloxide other than Al₂O₃ or CaO at least a portion of which at least aportion of which forms a distinct crystalline phase when the glass iscrystallized, and if the metal oxide other than Al₂O₃ is CaO, then theCaO is present up to 10 percent by weight, based on the total weight ofthe glass.
 17. Glass-ceramic comprising at least 35 percent by weightAl₂O₃, based on the total weight of the glass-ceramic, and a metal oxideother than Al₂O₃, wherein the glass-ceramic contains not more than 10percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, andV₂O₅, based on the total weight of the glass-ceramic, wherein theglass-ceramic has x, y, and z dimensions each perpendicular to eachother, and wherein each of the x, y, and z dimensions is at least 5 mm,with the proviso that if the metal oxide other than Al₂O₃ is CaO, thenthe glass-ceramic further comprises crystals of a metal oxide other thanCaO, and wherein the CaO is present up to 10 percent by weight, based onthe total weight of the glass-ceramic.
 18. The glass-ceramic accordingto claim 17 wherein the metal oxide other than Al₂O₃ is Y₂O₃.
 19. Theglass-ceramic according to claim 17 wherein the metal oxide other thanAl₂O₃ is REO.
 20. An article comprising the glass-ceramic according toclaim
 17. 21. The glass-ceramic according to claim 17 in the form of anIR window.
 22. A method for making glass-ceramic, the method comprising:heat-treating glass such that at least a portion of the glass isconverted to a glass-ceramic, the glass comprising at least 35 percentby weight Al₂O₃, based on the total weight of the glass, and a metaloxide other than Al₂O₃, wherein the glass contains not more than 10percent by weight collectively As₂O₃, B₂O₃, GeO₃, P₂O₅, SiO₂, TeO₂, andV₂O₅, based on the total weight of the glass, wherein the glass has x,y, and z dimensions each perpendicular to each other, and wherein eachof the x, y, and z dimensions is at least 5 mm, with the proviso that ifthe metal oxide other than Al₂O₃ is CaO or ZrO₂, then the glass furthercomprises a metal oxide other than Al₂O₃, CaO, and ZrO₂ at least aportion of which forms a distinct crystalline phase when the glass iscrystallized, and if the metal oxide other than Al₂O₃ is CaO, then theCaO is present up to 10 percent by weight, based on the total weight ofthe glass.
 23. A method for making a glass-ceramic article, the methodcomprising: providing glass particles comprising at least 35 percent byweight Al₂O₃, based on the total weight of the glass, and a metal oxideother than Al₂O₃, wherein the glass contains not more than 10 percent byweight As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the totalweight of the glass, the glass having a T_(g); heating the glassparticles above the T_(g) such that the glass particles coalesce to forma shape, the glass comprising at least 35 percent by weight Al₂O₃, basedon the total weight of the glass, and a metal oxide other than Al₂O₃,wherein the glass contains not more than 10 percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thetotal weight of the glass, the glass having a T_(g), with the provisothat if the metal oxide other than Al₂O₃ is ZrO₂, then the glass furthercomprises at least one of Y₂O₃ or REO; cooling the shape to provide aglass article; and heat-treating the glass article to provide aglass-ceramic article.
 24. A method for making glass-ceramic particles,the method comprising: atomizing a glass melt comprising at least 35percent by weight Al₂O₃, based on the total weight of the glass melt,and a metal oxide other than Al₂O₃, wherein the glass melt contains notmore than 10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the glass melt;cooling the atomized glass melt to provide glass particles comprising atleast 35 percent by weight Al₂O₃, based on the total weight of eachglass particle, and a metal oxido other than Al₂O₃, wherein the glasscontains not more than 10 percent by weight collectively As₂O₃, B₂O₃,GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of eachglass particle, wherein the glass has x, y, and z dimensions eachperpendicular to each other, and wherein each of the x, y, and zdimensions is at least 5 mm, with the proviso that if the metal oxideother than Al₂O₃ is CaO, then the glass further comprises a metal oxideother than Al₂O₃ or CaO at least a portion of which forms a distinctcrystalline phase when the glass is crystallized; and heat-treating atleast a portion of the glass particles such that at least a portion ofthe glass is converted to a glass-ceramic particles.
 25. A plurality ofabrasive particles having a specified nominal grade, wherein at least aportion of the abrasive particles is a plurality of abrasive particlescomprising a glass-ceramic, the glass-ceramic comprising at least 35percent by weight Al₂O₃, based on the total weight of the glass-ceramic,and a metal oxide other than Al₂O₃, wherein the glass-ceramic containsnot more than 10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the glass-ceramic.26. A method for making abrasive particles, the method comprising:providing a plurality of particles having a specified nominal grade,wherein at least a portion of the particles is a plurality of particlescomprising an amorphous material, the amorphous material comprising atleast 35 percent by weight Al₂O₃, based on the total weight of theamorphous material of each particle of the portion, and a metal oxideother than Al₂O₃, wherein the amorphous material contains not more than10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂,and V₂O₅, based on the total weight of the amorphous material of eachparticle of the portion; and heat-treating the particles comprisingamorphous material such that at least a portion of the amorphousmaterial is converted to a glass-ceramic and such that a plurality ofabrasive particles having a specified nominal grade is provided, whereinat least a portion of the abrasive particles is a plurality of abrasiveparticics comprising the glass-ceramic.
 27. A method for making abrasiveparticles, the method comprising: heat-treating particles comprising anamorphous material such that at least a portion of the glass isconverted to a glass-ceramic, the amorphous material comprising at least35 percent by weight Al₂O₃, based on the total weight of the amorphousmaterial of each particle, and a metal oxide other than Al₂O₃, whereinthe amorphous material contains not more than 10 percent by weightcollectively Al₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thetotal weight of the amorphous material of each particle; and grading theabrasive particles comprising the glass-ceramic to provide a pluralityof abrasive particles having a specified nominal grade, wherein at leasta portion of the plurality of abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic.
 28. A method for makingabrasive particles, the method comprising: heat-treating amorphousmaterial such that at least a portion of the amorphous material isconverted to a glass-ceramic, the amorphous material comprising at least35 percent by weight Al₂O₃, based on the total weight of the amorphousmaterial, and a metal oxide other than Al₂O₃, wherein the amorphousmaterial contains not more than 10 percent by weight collectively As₂O₃,B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of theamorphous material; crushing the glass-ceramic to provide abrasiveparticles comprising the glass-ceramic; and grading the abrasiveparticles comprising the glass-ceramic to provide a plurality ofabrasive particles having a specified nominal grade, wherein at least aportion of the plurality of abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic.
 29. A method for makingabrasive particles, the method comprising: heat-treating ceramiccomprising an amorphous material such that at least a portion of theamorphous material is converted to a glass-ceramic, the amorphousmaterial comprising at least 35 percent by weight Al₂O₃, based on thetotal weight of the amorphous material, and a metal oxide other thanAl₂O₃, wherein the amorphous material contains not more than 10 percentby weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅,based on the total weight of the amorphous material; crushing theglass-ceramic to provide abrasive particles comprising theglass-ceramic; and grading the abrasive particles comprising theglass-ceramic to provide a plurality of abrasive particles having aspecified nominal grade, wherein at least a portion of the plurality ofabrasive particles is a plurality of the abrasive particles comprisingthe glass-ceramic.
 30. A method for making ceramic, the methodcomprising: combining (a) glass particles, the glass comprising at least35 percent by weight Al₂O₃, based on the total weight of the glass, anda metal oxide other than Al₂O₃, wherein the glass contains not more than10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂,and V₂O₅, based on the total weight of the glass, and (b) refractoryparticles relative to the glass particles, the glass having a T_(g);heating the glass particles above the T_(g) such that the glassparticles coalesce; and cooling the glass to provide the ceramic. 31.The method according to claim 30 wherein the refractory particles areselected from the group consisting of metal oxides, nitrides, carbides,and combinations thereof.
 32. A method for making glass-ceramic, themethod comprising: combining (a) glass particles, the glass comprisingat least 35 percent by weight Al₂O₃, based on the total weight of theglass, and metal oxide other than Al₂O₃, wherein the glass contains notmore than 10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the glass, and (b)refractory particles relative to the glass particles, the glass having aT_(g); heating the glass particles above the T_(g) such that the glassparticles coalesce; cooling the glass to provide ceramic; andheat-treating the glass of the ceramic to provide the glass-ceramic. 33.The method according to claim 32 wherein the refractory particles areselected from the group consisting of metal oxides, nitrides, carbidesand combinations thereof.
 34. Amorphous material comprising at least 35percent by weight Al₂O₃, based on the total weight of the amorphousmaterial, and a metal oxide other than Al₂O₃, wherein the amorphousmaterial contains not more than 10 percent by weight collectively As₂O₃,B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of theamorphous material, wherein the amorphous material lacks any long rangecrystal structure as determined by X-ray diffraction, wherein theamorphous material has x, y, and z dimensions each perpendicular to eachother, wherein each of the x, y, and z dimensions is at least 5 mm, andwherein the amorphous material has a density of at least 85 percent oftheoretical, with the proviso that if the metal oxide other than Al₂O₃is CaO or ZrO₂, then the amorphous material further comprises a metaloxide other than Al₂O₃, CaO, and ZrO₂ at least a portion of which formsa distinct crystalline phase when the amorphous material iscrystallized, wherein the CaO is present up to 10 percent by weight,based on the total weight of the amorphous material, and wherein theamorphous material does not have a T_(g).
 35. A method for makingglass-ceramic, the method comprising: heat-treating amorphous materialaccording to claim 34 such that at least a portion of the amorphousmaterial is converted to a glass-ceramic.
 36. The amorphous materialaccording to claim 34 in the form of an IR window.
 37. Glass comprisingat least 35 percent by weight Al₂O₃, based on the total weight of theglass, and a metal oxide other than Al₂O₃, wherein the glass containsnot more than 10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the glass, whereinthe glass has x, y, and z dimensions each perpendicular to each other,and wherein each of the x, y, and z dimensions is at least 5 mm, withthe proviso that if the metal oxide other than Al₂O₃ is CaO or ZrO₂,then the glass further comprises a metal oxide other than Al₂O₃, CaO,and ZrO₂ at least a portion of which forms a distinct crystalline phasewhen the glass is crystallized, and if the metal oxide other than Al₂O₃is CaO, then the CaO is present up to 10 percent by weight, based on thetotal weight of the glass.
 38. The glass according to claim 37 whereinthe metal oxide other than Al₂O₃ is Y₂O₃.
 39. The glass according toclaim 37 wherein the metal oxide other than Al₂O₃ is REO.
 40. Theglass-ceramic according to claim 20 wherein the metal oxide other thanAl₂O₃ is REO.